I'm shooting 4" vanes with a slight right offset cock fletch down.
I'm shooting Gamegetter 2216's 28" at about 68# with 100 grain points.
The rest is a shoot thru type wth 2 prongs, I'm not sure of the brand but its a real simple rest.
What I think is happening is the rest is folding down as the arrow passes & the cock vane is hitting the rest between the prongs. I just dont know if I should give the rest more spring tension or move my nocking point higher. I use a caliper type release & my nocking point is about a 1/8 above square now.