I was throwing the non epoxy head flies last Friday and couldn't get it to swing from side to side. After much investigation on the fly for flaws, i was getting very frustrated on the crappy water movement. In came the tree. I ditched it in a tree by the bank and broke it off. We went to the bank to pick up the fly and i had to re-tie. I put on my normal 3 feet of leader and went to casting. The fly swung beautifully.
NOTE: I can only assume the shorter leader was too stiff and not allowing the fly to swing. I am now careful to not allow the leader to get shorter than two feet before throwing these flys. I save the shorter leaders to use when throwing the sinking line.