Jeez, thanks for the nice comments!

I'm hoping to cram a Saito 100 twin between the frame rails. It will sit pretty high and raise the CG quite a bit, so that idea is not set in stone yet. Also, in order to liquid-cool the twin, I would have to machine the cylinders down to add cooling jackets. The design of the Saito is such that it would be tricky, and the jacket would have to be kind of thin. I may be able to make it work, though. That's an expensive engine to hack into.