RE: 4 or 5 inch vanes?
I have been using carbons with 4" vanes and NAP mechanicals. Recently went with 3 blade Muzzys. When I would shoot the Muzzy they would consistently hit about 12" low and 6" left of my aim point. The field points were right where I wanted them to be. Went to Smithfield Archery here in North Richland Hills and talked to Stan. He suggested that I refletch with 5", a slight offset and align the broadhead with the fletching. I did that and they are dead on. No adjustment of my sights were necessary.
The harder I work, the luckier I get!