Good news...figured out a massive leak in the cooling system. Half part poor installation and half just a little fatigue.
I removed the trim panel on the ceiling and found the blower side with huge holes carved out directly over to the intake side. This looks like to run cabling but man did they leave a mess. I stuck some cardboard in there and taped it in place. Also found the pass through duct work leaking at the bottom.
The next thing was a very inadequate seal where the trim keeps the two sides separate. This was probably just from some fatigue of the plastic. A nice 1" thick camper tape type foam would have worked but I didn't have that. I folded up a new towel and stuck it in there.
After testing I found a huge increase in duct pressure, no cold air in the return side, and I think my weaker AC has improved. We are dry camping this weekend and it will be a good test.
Thanks everyone for your advice.