Not trying to derail where this conversation is at currently, but, I bought a JR extension for my Dynatron. It mounts directly to the starter shaft. I'm really not liking it at all because it's not dead straight and it vibrates like crazy. I wanted to go away from the one I had that fits in the rubber cup but now I'm thinking maybe it's not so bad since the rubber dampens vibrations. I was 100% sure I didn't want to spend $100 on the Sullivan one-way shaft but now I have decided to not entirely rule it out.