Any proshop that would make a blanket statement that any one fletching choice is best for all applications is speaking irresponsibly. For me and my hunting applications I shoot fobs. But from my traditional bows I shoot feathers (I have shot fobs though :wink

. On my feathers 4" works just as good as 5" and I have no doubt that 3" would probably work fine too. Sounds like your proshop has an overstock of 5" feathers they'd like you to take off their hands for them. The best part about having so many choices in archery today is taking the time to experiment a little, try different things and find the combinations that work best for you.