Another item you may want to look at.......AIR LIFT 25592 Load Controller II On Board Air Compressor System ($171.14 Amazon)
You can adjust air pressure on the fly, plus it has an adjustable low pressure sensor so you don't have to worry about bags being under inflated. Love the setup, when not towing bags are 5 psi, hook up trailer, crank them to 15-20 psi with dash mounted switch. After a day of wheeling, put the toys away and air down with bleeder valve (left of rocker switch)........easy peasy!