I center the pin. Dont even really center it, I just look thru my peep & put the pin on what I wanna shoot. I only recently started using a round sight housing & cant really see a reason to complicate things. People are different but it seems like alot to keep track of, centering the housing in the peep & them putting the pin on your target. But then I shoot alof of firearms with peep sights so it seems natural. I dont thing of the aperature at all, I look thru it & put the front sight on target.