Brian,
That looks a lot like the engine I have been designing (well fantasising about) in my head!
Thielert / Centurion looks more like it as well allthough only at 130hp plus.
So the engines are out there, the problem is the US manufacturers saying "We don't want any of that new fangled European technology here"?
Looking at the Luddite comments about structures as well as engines, I can imagine them saying to the Wright brothers that the Flyer was too hi-tech and that we should stick with Lillienthal hang gliders.
Incidentally, I love old stuff, I just don't think it should still be in production. Even with just a few hours training I am already fantasising that I would spend the big premium bond win on a Puss Moth not a Diamond Star.
Cheers
Joe