Thought I'd ask this here since I'm in this contest and trying to improve. I was reading Matt/PA thread on 3D shooting and read this:

Also stick to ROUND pin guards and peep sights that properly match the diameter of your pin guard. A proper fit allows just a small halo or ring of light to show around the outer edge of your pin guard when it is perfectly centered.

I would guess this to be true for any type of shooting . If so, my peep is too small.