Hi Harry,
Hands down I love the 50 size Sundowner the most. My first one was running a .95ax but it way to heavy, but it certainly was quick. It was fitted the same way as the Dubb Jett 60LXH and I used one of their tuned pipes. A .75ax will fit no problem but a little work will be needed. My latest Sundowner runs the Dubb Jett 60LXH, lite super fast and reliable.

http://www.jettengineering.com/sundowner.html