I have owned 2 pvs27s, 2 pvs30s, and an M2124-LR (CVS-LR). Without a doubt, the smallest shift was with the pvs27 and PVS30 units.
The L3 M2124-LR had a different shift based on the cant of the base or mount, so you had to pattern it to each gun. I didn't ever pattern one of the 30s and...