Not sure which type of truck you have, but setting the air pressure of your bags, here is what some of us do.
Camper off, measure the distance from the ground to the wheel well center.
Load the camper with everything you want in it fully wet and put it on the truck if it is not on already..hahahaa
Measure the distance and put enough air to raise the rear of the truck, ground to wheel well back to what you measured and that is it.
My truck is a 94 f250 460 gasser crew cab. My camper weights, fully wet and loaded 4200lbs
My bags only need 40psi to bring the bed back to unloaded height.
My bags are AirLifts.
Jim