Remember... the longer the fletch, the higher the profile, the further back it is on the shaft, and the more it's helically fletched, the more steerage correction the feather will provide. The downside (there is always a downside), the slower and noisier the arrow will be. That being said, I use 5" helically fletched shield cuts for broadheads, cuz I'd like to hit what I'm shooting at, and the trajectory is negligible. For pure target shooting, I use a 4" parabolic, with a 5 degree offset. Also, remember to offset to the feather wing, ie., if you're using right wing feathers, use a right offset. Never straight fletch for trad gear, you want the arrow to spin somewhat for best flight.