It wasn´t difficult at all. I just used some good quality balsa sheets of 1mm and customized them to the proper shape. I like the round smooth looking that it adds to the plane. From the middle to the back is ok with the sticks.
The Roto 35 seems to be a very good choice. I wonder how a 3 blade prop will help to smooth out the engine, you mean, that it will shake a little less or that it would reduce its pulling power?