RE: Rest for helical fletching????
I used to use full helical on my arrows, but not any more. I've found out that you don't need all that helical to stabilize an arrow, even with a big Magnus I head. All a full helical does is slow down your arrow speed and make noise.
You will get great arrow flight with 5" feathers by using just enough helical to still allow room for the prongs on a standard prong type launcher rest.