ORIGINAL: P-51B
I have seen some with the Irvine 53 and also the saito .72, both give better performance than the OS 50, IMO.
In the SSE instruction manual for the kit (maybe for the ARF also) it talks about engine selection and the difference between 2 and 4 strokes. They say, in their opinion, that the 4 stroke will work in the plane but they tend to be heavy. Have you seen or heard any pros or cons on this subject? Thanks, Gene