Surely, there is a simple (if a little long winded) solution to shooting in "thinner" air.
Thinner air will simply make your trajectory flatter. So to reform the original curve and restore your original zero, you have two adjusters to tweak.
1# The turret
2# The power of the gun
If you turn down the gun and dial in your original zero until the top of your trajectory is back where it was and the 55 yarder comes in back where it was, then surely all your original settings will be spot on?
Anschutz 2013 MEC1 .22LR
Miroku 3800 12bore