There are a few ideas I really like and want to explore: 1) Foam Frame cut by CNC with covering film. This seems to work really well . It is very light and strong. Covering film is normally used over a balsa wood frame. I had not seen it used over a foam frame before. This is lighter, more resilient in crashes, and faster/easier. So far this seems like a great method. 2) Wing tip motor/propellers. I think this will be extra efficient. I can't find either real planes or RC planes that have tried to get extra efficiency from this. The propellers will rotate in the direction to counteract the wingtip vortices on that end of the wing. 3) Differential thrust so no vertical stabilizer. With two propellers we don't need a vertical tail, so can get rid of this drag. Extra efficient. Other people have done this....