Hi I have the KW12 motors along with Xoar 17" props on my Heavy lift Vulcan X8 UAV frame. There are some problems with the KW12 prop adapters. First of all the axle is too short to properly tighten the nut into the axle. Or the Xoar is too thick Another, bigger problem is that at least my prop adapters were of poor quality. Two of the eight adapters broke before even tightening the nut propely. As a result I came up with a solution pictured below. The axle remains are still in the middle hole, keeping the prop centered. Two socket head screws are going from adapter to the motor itself and two more are first going through the prop, then through the adapter and into the motor. What do you guys think? Will it work?