Uh-huh, now the secret's out... ya'll see the roots of my engine design!

Seriously though... SERCEFLYER I'm curious. Why are you hesitant to machine a taper for the crank and prop driver? In my opinion, for the average home shop, there isn't a better way - unless you have a way to broach shaped holes like the square (Fox) or "D" shaped (OS FPs). I know tapers on prop drivers have been discussed and frowned upon here, but the fact is, they're really little fuss and they work.

Although I have yet to try it, another method is to use the tapered & split collet between the crank and prop driver - like on the majority of the engines nowadays. At least your crank could remain parallel and you'd only have to experiment with making and fitting (or risking) the small parts.

-Joe