Thanks for the info Bla Bla and to others for your positive comments and related expereinces! I'm finishing an engine test stand that will measure engine temp., RPM, thrust (in pounds of force) and fuel consumption. It's going to be interesting to see how various prop, fuel and engine combinations stack-up in getting closer to a more scale-like RPM and sound. We'll never get the same sound and RPMs as the scale jobs, but in my book, the farther away from sounding like a nest of hornets the better.