Great project!
Another engine suggestion would be the 26CC gasser MVVS1.6
with the tune pipe. Menz S 18x8 over 8200RPM at only 3 lbs!
The Funtana has already a tunnel under the fuse to fit the long pipe.
I am using that engine with Bisson pitt muffler but it chokes it. Menz S 17x8, 8000RPM. Very light combo
http://www.mvvs-nl.com/
http://mvvs-canada.com/product_category2.htm