Hello Mike,
Just a thought...are you worrying unnecessarily about the Dampa and the problem is elsewhere?
In no particular order, could your scope, local weather conditions,
rifle set up etc be the cause?
I had a .20 Eliminator/Weaver V16 (890fps/Premiers) until last year. Very smoothe/accurate and no POI shift.
Once zeroed, I don't think I touched the scope turrets again.
HTH, Regards, Ed