What Doc O Glock said... After verifying POA, I use an old Weaver Accu-Point to help me when I fit my hunting shotguns. If you're not familiar with the accu-point, the visible "bead" (an early fiber optic) is at the end of a very small hollow tube about 3 inches long...the only way you can see the bead is if your eye is almost perfectly aligned with the rib and tube. On a hunting gun or a gun shot from a low ready position, I don't really care if it has a bead or not after it's fitted.
On a target gun shot from a high mount position, I like the confidence that the twin beads give for lining up and locking in my postion - but a simple white bead works fine. After I call pull, I never consciously see the beads again - of course, I don't consciously or unconsciously see my name in the winner's circle very often so I'm not sure how good my advice is....