I use a Bitzenberger with a left helical clamp on Axis and Beman MFX shafting. If you place a shaft in the jig and "eyeball" an empty helical clamp on the shaft you will find it does not mate well to the shaft, touching at one or two points with noticeable gap along the rest of the surface. Next, carefully with a file (I use a 10" half round bastard)file the clamp down, checking progress as you go untill the clamp evenly along it's length contacts the shaft. You will find that you have plenty of offset and fletching taped or glued evenly along their length.