I've shot 2, 3, and 4 fletch, 4"-5" feathers, and both straight and helical. I haven't seen any difference, but I try to get my arrows very well tuned to my bow bare shaft before I even think about feathers. I think tuning is the real key. If you did a scientific test from a shooting machine at relatively long range with heavy crosswinds, shooting various sizes, numbers, and orientations of feathers, I'm thinking you'd find that more feathers, longer feathers, and helical fletch would be slightly more accurate, just because, in theory, that should produce greater spin, which should create more stable flight. But I doubt the difference in accuracy would be significant.