Just an update on the muffler. I decided to get one from Wacker engines. It seems well made, with clean workmanship. I ran it briefly in my back yard today and got a 600 RPM increase over the stock muffler I was using. It is louder, though I didn't expect it to be very quiet. My test stand has the engine mounted upright so I can adjust the carb and such easier. This points my exhaust tubes up right at me.

I still don't have a 20-10 prop. My pro zinger is now getting 8100 rpm. I think this could be improved on, but I really have not tried to fiddle with it too much since I've been busy building the plane for this engine. That and I don't have the prop I plan to fly with yet. Once I get it (prop), I'll do some more test at the field to get final best numbers.

Peter at Wacker was very pleasant to speak with. He got the muffler to me very quickly, and I am happy with the product and his service.