RE: 25 Size Engine?
I think for your pattern plane the OS .25FX or .32 would be the best choice. You can always add a pipe but I do not think you want Max RPM for pattern. Are you trying to go fast or have torque for vertical? I would even throw out the Saito .30 or .40 engine for this application. The .40 is basically the same size as the .30 and both are close to the size of the .25's. I love my little .30 Saito.