the piece I made for Kris^ is/was not designed to hold the prop on, it's a spacer to make the engine longer...It has the added benefit of keeping the prop from turning on the hub..Any hub can be drilled for 6 bolts if the hub is held onto a tapered crank with a nut, flush with the end of the crank....If the 2 anti-rotation bolts used on a single bolt hub are big enough and kept tight there's no reason they would ever shear off anyway...TIGHT is the operative word on any hub....