my bad guys, I just seen where I said a 150 psi pressure switch. I meant to say 50psi.
yes Bohall, the equilibrium comes into play. 35psi in a 3 gallon tank and 15psi in 2 bags, so when the air pressure in bags dropped i could bump it up to 15.
this is how I did mine. all in retrospect now, the return line didn't really do anything except when my tank was empty, for instance when i towed. added the extra 10psi to even the truck out thenloaded it and let the air out before unloading while the weight was still in the truck.