Hi and welcome to the Flying Giants. I have this plane with a Saito 1.80 and I have lots of power. A member on RCU has used a SPE 26cc with great success. He has said he has the same power as the 1.80 he used to have on it. If you go with a gas engine for this plane, I think your best bet will be the SPE 26cc. The Evolution 26 will not provide you with a lot of power, but give you enough. Below is QQ's article with his similar-sized Yak using the Evolution 26. Basically the engine provided adequate power, but did not give him the all out 3D performance.
http://www.qqaircraft.com/default.as..._page=evo73_hi