Last week I tested the TT46 out with a Hatori clone ... with a 9x8 I tached 15,500 RPM unfortunately the WM SS40 does not fly that fast so it was a waste of time. NOt bad for a 'cheap' engine. The 11x5 is a nice prop for 3D on this engine. I wish I could get a 11.5 x 4 here.