I am on the market for a simular plane. However, I was planning on powering with a 26cc. The SIG Rascal seems like a great plane, and would probably give you what you want if you were willing to go with a smaller engine.

For the 40cc, another option might be the Kangke 1/4 Giant Monocoupe. Ive heard of guys putting at 40cc in those with good results.