While I don't do it on the truck, I always inflate the trailer tires to the maximum pressure on the sidewall even if they're not at maximum load. Tires on trailers really take a beating and get hot, and I want every advantage I can muster to avoid any issues. In your case, I would probably not lose sleep running them at 65 psi, but I wouldn't do it anyway.
My truck actually specs only 75 psi on the rear for maximum load and I never follow that either because the truck needs all the rear tire capacity available to be able to carry the full GVWR, so I run those at 80 psi too.
Fronts I keep at the door sticker pressure, which I think is 50 psi. There's no need for more than that up there as most of the trailer weight is on the rear axle.