What I would do is load up the truck with all the normal weight, camper, trailer, water, etc. Leave the bags empty. Then slowly add air to each side until you come off the OEM overload bumpers. Then measure the wheel well on each side. Now let air out so you drop about . 75". This will keep you from losing contact on the overloads on rough corners and inducing a harsh ride, and it also keeps the OEM overloads in the game for stability and load carrying.
Take note of what the bags have in them, and then when you empty the truck take note of the pressure as well. The pressure will drop considerably when you remove the weight so you need to know what it is empty so you can be prepared for the next trip.
I let my suspension drop about 1-1. 5" when loaded, that takes about 5 psi in the bags empty for just the TT, and about 8 psi in the bags empty for when I have the quad in the bed and the TT.
The 5 psi goes up to about 15 psi when loaded and the 8 psi goes up to about 25 psi when loaded.
Don't ever set the bags over about 60 psi empty or you could blow them when you put a heavy load on.
This is what I do. Measure the distance from the ground to the top of the wheel well while unloaded. When loaded, fill the air bags until you are back at that height. Now your springs are working where they started off. It works for me but I need the full 100 psi with my 5th wheel. My truck is much more comfortable to ride loaded than empty.
I do it very similar; however, I prefer to let the truck sag an inch or two to get more weight on the OEM springs and bottom overload. I don't like all the load resting on the airbags, the ride is much harsher riding than it needs to be. I see people do this all the time, and they never seem to like their ride. Take about 20 psi out of the bags and see how it goes.