RE: Moving engine forward changes geom'ery?
My move was purely for balance. 3" is a lot, but the EAA Bipe has a very long nose and can stand the shortening. In the end, with my Echo 21cc mounted, I was lead free. Nice!
I might have gotten away with using the OEM cowl, but by the time I modified my plane, the cowl was crap. I scratch built my own glass version ... another story that.
Still one of my favorite flyers, but it is currently stored 7000 miles away, so I don't get at it much.
Enjoy,
Bedford