I always thought the main advantage of 4-fletch was that the arrow was always oriented properly on the string. Never tried it myself. Logically, one could go with smaller vanes and still have the same total steering surface, I suppose...
Makes nocking an arrow possible without having to take your eye off your target (or if you're shooting in the dark
). With traditional gear, I used to shoot 5 to 5-1/2" 3 fletch on wood shafts (and still do at times), but mostly shoot 3-1/2 to 4" 4 fletch now with wood and carbon and find it to be plenty of steering surface.
