For two up flying, just strip down some of your old slot cars for the motors, or better yet, some of the electric motors and receiver/speed controllers from some small, cheep R/C sport flyers. Then fly them using the throttles to control altitude, and if you have a second channel, add elevators. This has been done commercially in a similar manor but a good modeler ought to be able to build something better. Might not be stunt capable but still fun to race, slice and dice a round with. If we were still a long way off to flying season I might work on something like that!
Type at you later,
Dan McEntee