It's all personal preference, really.

You will notice though that, sometimes, the further your pins are away from the bow the more accurate you'll shoot. This isn't the case with everyone, but for some people that's just how it works. Try all the distances to figure out which works best for you.

Personally, I shoot best with it mounted using the middle set of holes. However, I don't center my pins in my peep when I shoot, I line the rim of the peep on the rim of the sight.