I goofed. When I was building the balsa cowl I was less than 1/8" too long. When I put the spinner backplate on it rubs. The front of the cowl has a 1/8" inch plywood ring in the front, so I can sand it down but just a very little. Is there some kind of spacer I can put between the drive washer and the spinner backplate. Or is there another option. I would hate to remove the engine and put spacer behind the motor mount. It is very difficult to get to. This is a magnum 180 4s.