I would like to go with the OS 50 for cost, of course. I also have a Perry pump, but it is about 8 years old. Come to think of it I have a Pitts style muffler that might fit it too. Hmm. Maybe that's the way to go. I really think the .61 will be too much.

I too have never used a 4 stoke. 1 consideration though is that a 4 strokes stock muffler will work. The 2 strokes mufflers will not. An OS 50 with a Pitts style muffler is within a few bucks of the Saito 72 though. I have always heard from everyone that uses 4 strokes they like them better.

jwatwood have you tried to hover with the OS 50?