BTW, I don't know anything about the size or weight of the Dynaflite model. But my 1/6 scale SE5a uses a Saito 56 4-stroke and that's plenty of power. So I'm wondering if a Saito 120-size 4-stroke is "too much" for your model. Would a 90-size 4-stroke be enough for your 1/5 scale model? What do the plans call for? You might also want to check on people who built the FunAero SE5a.