This should work
http://www.homebuiltairplanes.com/forums/aircraft-design-aerodynamics-new-technology/5683-development-dream.html
Every builder is searching for that most elusive animal..............the most suitable power plant. Lots of good ones available but we can all find problems with them, usually, cost, or in the case of 2 strokes, noise.
Not into UAV myself but yes, I guess that is 'out of the box'.