Old thread, but I just went through something similar. A ring height that put the optic “centered” with the pvs-30 would put the optic too high for comfortable day shooting. After speaking with people with a lot of time behind pvs-30’s and 27’s I was told “as Long as you can see through the optic, then the alignment is good enough”.
My day optic centerline is about .400” below my pvs-30 centerline and my day optic is canted 20 MOA down relative to the pvs-30 (day optic is on a 20 MOA rail while EFR i parallel to the barrel). I have about .3 mil POA/POI shift, which is consistent with “perfectly aligned” setups.
The collimating on the PVS 30’s is VERY tolerant. I’d actually be curious if someone built a rig to test just how tolerant they are. I would imagine you get pretty far out and still retain POA/POI.