To the OP, your lower pressure issue should not be of any concern. I'd be more worried about the chance of a termite climbing into the back of my truck and chewing up the wooden leveling blocks I carry (ie...not worried). I intentionally run the air pressure in the front tires of my diesel pickup at 65 PSI, though they're rated for 80 PSI. LOTS of people do this because it helps with ride, control, and stability on the HD trucks. On my equipment trailers, I run MAX pressure because, well, they're loaded down. 500 miles spread over 3-4 trips at 50 PSI...pa-lease...
Now, all that being said, I would agree that you DO have a problem if your trailer is loaded to max (or beyond) or if you're running super cheap China bombs (not all made in China tires are bad) or you should be running load range E instead of load range D (which is what you have). When I got new tires on my 5'er, I skipped straight to load Range E so I don't have to worry about all this stuff.