This is scale project. First I was thinking about 4-stroke (Ryobi) for it, but as there is no benefits from it, I decided to use common 2-stroke conversion.
The original Wilga is very slow plane: stall speed is 40mph, cruise speed is below 90mph. There are not so many pilots allwed to do a loop on full scale Wilga and roll is plain impossible. The plane is used mostly for sport flying and glider towing. Sometimes for skydiving, but only 3 guys (plus pilot) can fit in there.

So my 1/4 scale (actually 22.5%) should take off at 10mph, and fly at 20 mph and be able to fly straight and level.

RysiuM