I have had two different RCGF 46cc gas engines and an NGH-38GF gas four stroke engine in my Sportster and those three engine flew the plane quite well. I am now moving on to a DLE 55-RA rear exhaust two stroke gas engine. I know that it will be a bit over powered but should be a lot of fun to fly.
Best wishes and good safe flying.
Heli-NuBee (AKA Roger the radial rabbit)