LAST EDITED ON Jun-27-11 AT 09:14PM (MST)[p]The body angle between 50 and 80 changes rapidly with distance. This causes the peep height to effectively change. It's not really a anchor change so much as the string angle from the shorter shots to the longer ones. This is probably not the biggest issue though.
You probably have your longer pins low in the sight housing. This is making it difficult to keep the peep, housing and pins centered and you then start to center the pin in the peep instead.
I switched to a slider sight for that very reason. I put four pins up high with the 50 yarder right in the middle of the housing. That way all my longer shots have the peep, housing and pin perfectly centered for all shots of 50+.
Anyway check that peep/housing alignment to make sure you aren't going skiwampus on those longer shots.
Cheers,
Pete