The loads may not be as high as one thinks... I flew many hours with a Phantom Ultralight airplane with a Kawasaki 440, 40 horsepower engine. I later put a Rotax single carb 46 horsepower engine on the plane, and again flew it many hours, using the same prop reduction drive. The reduction drive was nothing more than a 7" multi groove "V" belt pulley, with two ball bearings in it running on a 3/4" diameter shaft. The bearings were actually in the pulley, and no more than about 3" apart. The pulley ran on that 3/4" shaft, that was on an eccentric for belt tension adjustment. The belts ran from there to a corresponding 2.5" pulley mounted to the engine PTO. The engine(s) turned around 6500 rpms or so, and swung a 60" adjustable pitch prop with the pitch adjusted to dial the engine in to it's rpm range. I didn't do actual aerobatics in that plane, but I was quite agressive in how I flew the plane, and never had a problem with the reduction drive system.

That is why every time I look at the Tony Clark reduction system, I wonder why they think they need a rotating shaft with bearings spaced far apart for the prop shaft/pulley. A lot of unnecessary extra weight from my way of looking at it...

AV8TOR