I checked the four bolts attaching my AC to the top of my 28.5RLS fifth wheel today. Two of the bolts had never been tightened at all (about a half inch from the head of the bolt to the metal) and two were tightened; the tightened ones were at diagonally opposite corners. It appeared that the gasket was compressed properly in all four corners of the AC, judging by the yellow indicator. So, I guess, this means that the gasket is tightened enough to prevent a leak -- although just tightening two bolts seems sloppy.
I will ask my dealer to check this, and I will ask him to talk to Jayco for an explanation of what the official procedure is to tighten down these bolts.
By the way, on another fifth wheel we owned (a Sunnybrook) we had a leak at this gasket. The issue was that when the AC was attached to the trailer during construction, the installer did not remove the shipping blocks. So although the AC bolts were tightened, the gasket was never properly compressed because the shipping blocks prevented it. Of course this was after the warranty was expired, and Sunnybrook would not do diddly.
So I'm a bit sensitive to this issue, and will get an explanation from Jayco.