I have had both the Yellow Aircraft gear and Sierra Precision gear in my Yellow Spit and in my opinion, the Sierra gear look better and are stronger than the Yellow gear. The Yellow Gear are pretty, better looking than the Robarts, but just not as nice as the Sierra gear.

Regarding the engine, that is a very personal decision and varies a lot based upon flying style. For example, a G38 will fly it fine, but is not enough power for my tastes. I have a FPE 40cc in mine. I think at least a 50cc engine would be better, especially if you like flying long climbing turns. As others have said, extra engine weight is no problem. If I was doing it again, I would look at a 60cc engine, such as the 3W60 or something similar.

Ed B.