Running the max pressure just because is silly. Look up the proper inflation for your tires with a load inflation chart provided by the manufacturer. Since your load is well under your rated axle weight I suspect that 65 psi is more than enough. Increasing the pressure will only wear out the center of the tire faster and provide a harsher ride.
My truck with camper on it weights in at 13,140 pounds with about 8,800 on the rear axle, that's 300 pounds over the RAWR but the tires will support that weight at 70 psi according to the chart so that's what I run. When I hitch up the boat it adds about 400 pounds on the rear axle. I increase the pressure to 75 psi when towing the boat. The truck rides really nice and the tires are wearing extremely well. I've gotten over 50,000 miles out of these tires and they still have a lot of tread left.