RE: Helical vs. Offset
I have went around the world with fletchings and arrangements for years ! I shot feathers on an offset for the last 3 years and just switched back to vanes with a hard helical this year !
An offset IMO is fine for target shooting and expandables ! It can also work with fixed blades........but IMHO........nothing works better ( accuracy wise) for fixed blade heads than a good helical........assuming your getting good rest clearance !