It may be possible to fly a 50 gasser on a 15cc, it would most likely take a whole new frame, nothing big. I would also think only mild aerobatics, unless maybe some additives pep it up. Then it will cost more for fuel but still much cheaper than $25 to $35 a gallon.
I heard talk that there are two producers of glow fuel. Maybe time to start that glow to gas engine conversion. Hobby People was working on a Magnum glow to gasoline conversion, I think a 60 size. The project has been stalled over a year now.
I wish they would get it on.