Myself and the guys I fly with have had many of these 1/6 sig cubs over the years. They fly very well on smaller power plants. I think the standard 40 4s will give you very good performance. Watch the weight though. I spite of a lot of building on this plane and its predominately stick type construction, it is a very rigid plane. I covered mine with yellow Monocoat (Monojunk). If I were to build another, and I will, I would use Koverall and Polycrylic with acrylic latex paints and a clearcoat.
JEB