Ok so I took the AC cover off and I see the previous owner put caulking around the outside of the AC around the front and side edges and left the back with just the gasket. I loosened the nuts inside to see if there was a previous leak but the gasket is solid all around. Actually looks fairly new and I dont see any damage behind it. Is this a common practice or should I strip the 3 sides down to the roof? It looks like it may have been done the same time as the gasket if I were to guess. It doesnt go all the way back on the sides. It stops about 2 inches in front of the coil and the whole back side is free of any caulking...I'm assuming to let the ac drain.
Is it a common practice or recommended? NO.
But, were it me and not leaking, I would probably do nothing. At first sign of water either from rain or condensate, I would pull it up and do it right.
I'm thinking cut out the front 2 corners and where the roofline is lowest?
IF (ya, may be a big IF) you have a helper and a 1/2 sheet of cheap plywood and a new gasket, and are going to do anything, just pull the unit and replace the gasket.
The upper unit is not that heavy-- just bulky, hence the second person. The plywood is to set it on the roof without scraping anything while you clean up the opening.
On installation, compress gasket to 1/2 its original height.
Done.
The unit does not have to be pulled. It is actually a very simple procedure and can be done by one person. 'Cuz I did it. Undo the bolts on the underside (inside the motorhome). You will also have to disconnect the electrical connector. Go up on the roof, remove the shroud and ROLL the AC onto is side. Remove the old gasket and use a new gasket or that rolled sealant sold at Home Depot (my choice). Carefully roll the AC back in it's hole and tighten down the bolts.
I see some sagging between a few of the roof beams of the fiberglass. Not soft...is this a normal thing? You will have to blow up the photo to see...toward the front
Unless it's causing a issue I would leave it be. As long as your ac condensate is exiting the roof and not pulling up near the AC unit, let it be.
Does look like your roof has some uneven areas. take a straight edge across it and take some pics.