Answer

Do you have a fan ventilating your attic space? If you do, this would be making the attic more humid than normal. Try tuning this fan off.

It seems to me that you do not have enough air moving through the unit. I say this because everything is sweating, not just the old flex. This smaller amount of air gets colder than normal, and causes stuff to condensate. As an experiment, try running the unit for an hour without a filter in the filter grille. This will increase the amount of air moving through the unit. If this stops the sweating, you will know better how to solve the problem.

Feedback

I pulled the filter from the 20x20 return and let the unit run for a little over an hour (there is no filter by the air handler so it was the only filter).
Still condensating heavily. I took a picture or two of the plenum box that leads into the 16" return flex the dimensions are 19x9. Not sure if that is sufficient to feed a 16" return although the problem may be elsewhere I am going to be a little upset if I doped a sizable chunk of change to have that return redone and it was not sufficient.

This is the inside of the plenum triangular box that is the return for the 16" flex, showed in previous pictures.

Going to keep bouncing ideas and looking for a pro in the area who knows what he is doing, again thanks for the input/advice.

Answer

Here is my 2 cents.
There have been many good suggestions in this thread and this looks like an epic battle to weed through the hacks to try and get some qualified help. I think that your solution starts with only paying for the next guy if he suggests and carries out the basic tasks to determine why the system is unhealthy. If they don't talk this language, pass.

First, the basic tasks of charge level. Make sure that he/she will measure (as a minimum) the superheat if you have an orifice metering device or subcooling if you have a thermal expansion metering device. Gauges and PSI are not enough. A good tech will also measure condenser air dry bulb temp, indoor air wet bulb temp, delta T across the coil (return intake to closest grill), delta T through the condenser, etc. and be looking at some charts. If they are not hooking up a temperature probe to your refrigerant lines while measuring pressure then there is a problem.

Next, the basics of the airflow. They need to be talking about poking some holes in your ductwork (and possibly your cabinet) to measure static pressures in both the supply side and the return side with all of the normal filters in place and the supply registers all set as they are with the problems. The procedures are beyond the scope of this post but these pressure reading will let the tech know how balanced the outflow and inflow side of your system is (supply restrictions, return restrictions, filter restrictions, coil restrictions, etc.). If these readings indicate a system that is struggling because the blower capacity is mismatched to the system pressures, further investigation will determine where the problem is (dirty coil, restricted return, etc.). I am with so many of the other posters here in thinking that the rats nest of supply trunks may be choking your system but we need to stop guessing (on the return as well) and get some static pressure readings. The simple act of only stretching flex duct to 70% of it's design length instead of 95% during installation can cause a dramatic increase in air flow resistance and cause the air handler to struggle. Bends, kinks, sags all make it worse. These things are difficult to quantify by looking at web photos.

The Plexiglas door is a great suggestion. Get some measurements off of the door, go to home depot and get a door cut from some cheap plastic sheet material that will either sit in the door recess or be taped to the box frame. Have it ready for the guy so that when he shows up, it's another 5 minutes and no logistics for the tech.

Make sure that your drain is flowing without issue. The next time the door is off, pour some water into the drain channel in the cabinet and make sure that it flows out the drain line quickly.

Verify through a dealer authorized for your equipment that the outdoor unit is matched to the indoor unit, although a dysfunctional mismatch will show up in the above tests.

I agree wholeheartedly that you need to find out why a unit that is supposed to be less than 1 year old has a coil that looks this bad. It may be all the water flying around and improper filtration/attic infiltration but this thing looks many years old. I would ask for the serial number laden receipts and verify the sourcing of the units from the supply house.

Find out if the cabinet insulation is saturated with water. If it is, there is virtually no R-value left and that will contribute to cabinet sweating. After everything else has been corrected, the insulation will have to be replaced.

I will leave the choice on the lawyer up to you, but you can't get anywhere without this info so that you know why this system is so broken. You still do not know whom to pressure.

Feedback

074 instead of 068.

Finally found a decent pro, paid a premium as he does not work in this area but worth every penny, he checked static pressure .25 + .25 = .5.
Checked TD right on the $
But levels were off and water was POURING off the coil, about 4 hours later I asked him what the small plastic bag was attached to the compressor.
Low and behold, the 068 piston was supposed to be installed instead of the 074.
So again, the original installation company put a 3ton unit in with a 12' return, ductwork that was 25+ years old on the supply side, AND USED THE WRONG SIZED PISTON THAT REGULATES THE FREON, MAKING MY UNIT BLEED WATER ALL OVER MY ATTIC, RUN INEFFICIENTLY AND COOK MY FAMILY FOR ALMOST A MONTH!

Contacting the installers today and letting them know they will be paying for yesterdays service call. Have not decided about the increased electric bill, damage to the attic and bedroom ceilings from the water, and miserable couple of weeks they put my family through. In a way I hope they give me some static about just paying the service bill, think it might be just enough to put me over the edge

I was able to work something out with a local HVAC company and had the ductwork replaced.
Knock on wood the HVAC unit is one more thing that does not need to be dealt with for a while.

Again many thanks, I won't be posting as much but I will be doing some reading about other issues.

The airflow has been significantly increased, and I know this new set of ductwork had 1/10th the bends that the other had. Not to mention this new ductwork is not ridden with holes etc.

I know the best option would be to replace the entire flex ductwork system with a permanent metal solution, but that is not really feasible.

Lucky for me last year when it was warm I bit the bullet and went with the best HVAC company around (the most expensive too I might add) not only did I get them to fix the problem but they talked me into purchasing an extended 10yr warranty for the unit.

So after replacing the return and all the supplies this year when it got hot down here I went up into the attic and low and behold wet again, "whew" I thought good thing for that warranty.

Called the company up, they came out replaced the coil, replaced the drain pan, and took out the piston Freon regulator and replaced it with an exterior bulb device.

Problem is it is still sweating/dripping from the bottom, I called them up again and they said that "they were about out of ideas" which is a little concerning. They are going to come out in a few days and slide a piece of duct board under the unit (between the blocks supporting it and the metal of the unit) to better insulate it and have me run nothing but the fan for a week (which I am sure will make me very popular with the Mrs.).

They said if that did not work I would be "out of luck" anyone deal in warranties know if this is the point where I just have to level my house and rebuild?

The supply/return is all new and the warranty is supposed to cover the compressor and the furnace in the attic, if one of those 2 things is not working correctly can they just walk away?
I would not be quite so upset if the "warranty" was not so darn expensive, and when I purchased it I asked the lady who sold it to me:
"I am by no means an A/C expert but basically if anything goes wrong with the big box outside, or the big box in my attic between you and Goodman it is completely covered, right? I know it will not cover any of the ductwork but that is brand new anyway, as long as it covers those 2 units and the piping between them that is fine".
Her response:
"It sure does sir, you won't have to worry about it again, if something happens we will take care of it".
Now that something has happened and it does not appear to be an easy fix what I get is. Well, the warranty covers the units if something breaks, right now all the parts are working and static/temperature levels are acceptable so that is about all we can do.

This is the time that I would have gone BAH I should have paid the extra to get a good warranty with an reputable company instead of trying to save a buck, but this time I did go with the "best of the best".

Sorry for the 3 page revival of this post but I had a lot of helpful suggestions when working through this and ultimately went with the best, highest recommended, most expensive local professional company around. At this point if they walk away, I am not sure whom to call.

They did check the static pressure and temperature drop they were both within acceptable levels
(I guess the only thing unacceptable is the fact that I have water in my attic and am going to have to re-drywall, paint, and texture a ceiling again.

Answer

Looks like your bottom of the air handler is reaching dew point and is sweating or the drain is not draining properly. Is there a proper drain trap in the line? Also, you stated the static and temp drop was correct, what was the TESP and temp drop across the unit?

It may be that the Goodman air handler is not insulated enough to keep the temperature of the cabinet above dew point..
Can you build a room around just the unit and insulate it and make it part of your conditioned space?
If the unit has the proper drain trap is there a vent after the trap to make sure it is not double trapping somewhere in the lateral run which will prevent it from draining properly?

Feedback

Thanks for the response J, I had not thought of building a room around it to keep it cooler.
Not sure if I have this right but the difference in temperature between the return at the start of the unit and the supply where it comes out was at 17-18 degrees.

There is a proper drain trap, the HVAC Company checked the entire drain line for a double trap and during the course of this I educated myself on what to look for and there is only one P-Trap style trap on the entire drain line.

The drain pan has been replaced and when they ran the unit without the side on it, it appeared to drain correctly, when the unit was sweating and the side panel was pulled off the drain pan did not have enough water in it to indicate improper drainage.

Just got a voice mail from the HVAC service company I have my warranty with, they said the reason the unit may be having trouble is because it is in an attic and they may not be able to fix it.
Not sure why a company would install a unit in a place that it could not function or warranty one knowing that, seems a little fishy that I have 10-15 neighbors who have a home built by the same builder, same insulation, roof, plans etc and have units in their attic without forming a pond.

A couple quick things:
First off I have been out of town for a couple of days so I did not have a timely response to some of the posts.

Next apologies to Crmont, I had a DPIH High Humidity installation kit installed last year after you recommended it, after reading through the post I failed to mention it and for that I sincerely apologize, in my line of work there is nothing more frustrating than someone trying a solution and then not reporting the result. I most likely forgot to mention it because it was a $(self edit, it was more than my last dinner out to a nice restaurant for my wife and I) piece of flimsy, cheap looking, foam that after installed and the unit got dried out did nothing to correct the issue and left me feeling all the more disgusted.
It also was interesting that the installer had never heard of the DPIH and it had to be special ordered, it was not even carried at the local distributor.

The P-Trap is 4inches away from the drain pan, the drain pan (inside the unit) has been replaced and every time the side gets pulled off there has never been standing or impeded water in the pan.

Beenthere, today I had them check the static and drop again, .24 and .25 the temperature drop was 18 degrees, I did a lot of over the shoulder looking today and it was as they said as far as I could tell.

Mleonhartd, I took the manual up today and also made them recheck the dip switches while I watched.

The latest attempt to fix the problem was today, and it involved me helping 2 techs lift the air handler and slide 1.5 inch duct board under the unit to provide extra insulation.
A word to the wise, that stuff is way worse than batt insulation, wear something more than a T-shirt if your going to be rubbing your arms on it while you help someone slide it around, and to you DIYers just stay away from it.

Here is the latest picture with the foam board, they did not put in a vapor barrier like the one I suggested (thanks for that suggestion plick27 btw) but they put the foil side up which they said would act as one.
The real kicker is they said that after this they were "out of ideas" that I might have to get a new air handler, install it in my second bedroom (which is small so it would take up the whole thing after supply/return was run).
All of that would be at my expense of course because unit relocation is not covered by my "all inclusive" warranty. My question is:
If something does not work and I paid a pant load for a guarantee for them to keep it working for 10 years. Does it make sense or is it ethical that I would get stuck with the expense of new equipment and tearing my house apart if they can not figure out how to fix it, and I would still have to pay for the warranty?

On another, not I am thinking about going into the warranty business, I will sell high priced warranties then make a couple attempts to fix it, if it is not easy and inexpensive to fix I will tell the customer that I am "out of ideas" and they should buy new equipment. Who wants to invest in my business =)
Edit: (The above sentence is a sarcastic joke, not a very good one I might add, please don't send me PMs telling me that is a bad idea for a business and no one will invest)

Back home and up late because it is 85 in here, that is the lowest they said to set the AC for the past 7 days, tomorrow they are going to a new DHIP insulation kit as the first one completely saturated, the ductboard is in place under the unit.

The drains have been tipple checked they p-trapped correctly and water flows out of the drain pan, into the pipe and outside without any gurgling through the p-trap.

I set up a camcorder with a light on it inside the unit because they did not use my Plexiglas idea, we reviewed it and it did not seem like water was flying around on the inside.

Tomorrow is the long pass and hope for a touchdown, the unit has had the fan on and been set at 85 for the past 7 days, a new insulation kit, and ductboard underneath will hopefully fix the problem. If it does not at least I will not have to worry about it, because as hot as it has been if I can not turn the AC down to at least the mid 70s my wife is going to kill me.

The suggestion after this is for me to pay to have the unit moved into a closet (that will completely wipe out a closet in our 2nd bedroom) and put the furnace in there, they estimated it at around $more than my last mortgage payment to do, on my dime of course even though the thing is under warranty. May have to call Goodman after this, been dealing with this issue for over a year!

Feedback

The HVAC Company just left after installing both the duct board under the unit (pictured below) and now a new DHIP insulation kit, which is basically a 1/5 inch thick foam with a sticky backing to allow it to be attached to the bottom of the drain pan, which they did.

So the above two fixes are the most recent, the unit has been set on 85 for the last 7 days, with the fan on 24/7.

They hope this will fix the problem, and if anyone has lived in a house that is at 85F, with humidity that never went below 85% you feel my pain.

It is now 79 in the house and dropping, feels amazing just hoping that the issue is fixed as it has been miserable between the heat and the humidity here, especially working from home.

I should have an update in the next 24 or less, if it is sweating, thanks for everyone's contributions to this thread and suggestions, wish me luck I will keep anyone interested in this thread updated.

I think this picture says it all.
After about 15 hours of having the temperature set to 77 the unit is sweating, and the duct board underneath is saturated, comprising its insulation value obviously. 

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