All the rpm numbers stated above are starting to reflect something. It seems that they are in line with most of the other 50cc engines. When I was doing some prop testing with a Brison 3.2 at an elevation of about 800ft msl I was getting 7,300 with a Zinger 22-8, 7,100 with a Mejzlik 22-10, and 6,900 with an MSC 22-8. Hmmm...