On vehicles equipped with lt tires, I believe that the psi on the door jamb is set according the the vehicles gvwr. I contacted my tire manufacturer and got a load/inflation table for my tires and then weighed my truck with and without my Jayco. As I suspected, when running empty or even loaded my pressures were all too high. They did correspond with the max gvwr though.
Higher psi would give the opposite effect of a 'comfortable ride'. Also, wouldn't higher psi reduce your traction patch since you will be riding more on the center of the tire? Not to mention, wearing out the tires faster as well.
I run lower psi when empty and air up for towing, I am still below the 'vehicle manufactures suggest psi' even when towing, but in line (erring on the side of caution and leaving margin to add more weight) with the tire manufactures parameters.
1998 Jayco Eagle 302FK (Honda EU3000is)
2016 GMC Sierra Denali 3500HD 4x4 Duramax/Allison
2003 Honda Aquatrax F-12X Turbo