TPMS adds another dimension
I run a 2300 GMC 2500HD with newish Toyo Open Country CT's on 20" wheels. Sidewalls say 85psi max. I normally run the tires at 65psi front and 85psi back. Recently while the snow is on the road and the TT is off the road, based on a different forum and some sage advice, I decided to run all 4 tires at 65psi to improve the ride and maybe the grip while we are unloaded. Right away I got alarms from tire pressure monitoring system warning that there was low pressure in the rears. I found out that I have to keep them at 80psi or higher so I don't get the alarms. So, even if you want to "de-rate" your pressures based on loads, it looks like the TPMS won't like it.
On another note, when I had tires rotated last year, I had a lot of trouble reprogramming the TPMS. I tried the solution I found on youtube (turn the key, hold the remote control buttons, deflate tire until horn blows, etc) but no luck. In the end I took the truck back to the tire shop and it took them an hour to sort it out. Turns out they don't like TPMS for this reason. Any better ideas for reprogramming the position of the TPMS?