I use the axle spacers on the right side with and axle collar on the inside of the RR bearing. Basicly, the right side is locked. The left floats. If you don't let one side float, the chassis has a tendency to bind up.
I float the right side on my 2007 Velocity and the left is held with an Allen bolt that goes down into a tapped hole in the axle, simple and less parts, works for us, Sat. we sat on pole at Daytona Yamaha race.
I use thin wall 1 1/4 inch tubing that goes over the axle on both outsides of frame. Something that I learned when Stevie was runnin 1/4 midgets. I have never had a wheel or axle move since I started using them. Steve Sr.