i' ve been running a slot fin on my 66 rs1. the binding are in the stock position. i m not very consistant on this set up, nor was i on the original fin. i can get thru 35 pretty consistantly but 38 is nearly impossible. i was digging thru my box of fins. i found one that has a squared off back. i slapped it on and ran some pretty decent passes. what does this fin do that the round one doesnt..thx cs