Chuck,

Just to put a fine point on this issue keep in mind the pressure regulator has no impact on airing up the air bags when the engine is running. Your aux system pressure with the coach running peaks out at the bus air compressor set point which should be around 120 to 125 PSI.

When the key is off, and the aux compressor is the means by which you maintain aux system pressure it has no impact on your air bags because with the key off the air in the air bags is "locked" in. If you are trying to level the coach solely with the aux air compressor (key on, engine not running) then the aux air system and air bag pressure are going to parallel one another.

As to aux system pressure, I keep mine low, 80 cut out, 40 cut in because all the air operated devices I have in the house work fine at those levels. The lower I go, the easier it is on the compressor.