Dar, I've read the article, but I've also personally lived with both of those engines. I have found that the GP generally outpulls the Pro with most decent-sized props. The Pro works a little better in high-rev applications, where it actually will slightly outperform the GP, but in most real-world situations, it is the other way around.

I'm not criticizing the TT 61 Pro -- IMO it is better than the 61 FX -- it's just that I think the 61 GP is better that either one of them.

The one thing that I dislike about the GP is the air-bleed carb -- pretty low tech & not as easy to set-up for smooth transitions -- but then again, the engine is a simple plain bearing machine --- one that really works well.