I use 3 4" feathers with just about all my bows/arrow combinations, and get great flight with the heads I use. Like others have said, I think alot depends on how well the arrows are tuned to the bow. Of course, an arrow with 5"ers can be tuned equally well, and would probably offer more security in the event of a bad release, wet feathers, etc. But, fletch clearance is a factor too, and I tend to come down on that side. I usually shoot off elevated rests, on bows that are cut past center though....