I shoot three fletch for a couple of reasons: I like the way they look, and they're slightly faster to build.

I always use indexed nocks so it's easy to orient my arrows cock feather out without looking at them. In fact, the last three sets I built for myself have all three feathers the same color.

I have noticed that if I shoot an arrow with the cock feather in I don't get any difference in arrow flight. A couple weeks ago I was shooting a friends arrows to see how they flew in a bow and I wasn't paying attention to how I was putting them on the string. He had indexed nocks so I was going by that. It wasn't until I'd shot a couple dozen times that I noticed he puts his index to the inside and I'd been shooting everything cock feather in. I didn't see any bad arrow flight in all that.