I know some people have added helper air bags with an air compressor on the rear suspensions of their gas coaches that have low clearance for use exclusively on entering and exiting steep driveways. The advantage of the helper air bag solution is it works everywhere, getting in and out of gas stations, campgrounds, etc. Flip the in cab switch give the compressor a few seconds to pump up the air bags, drive over the hump, flip with switch off, which turns off the compressor and opens a solenoid valve to drain the air bags and be on your way.