RE: Combat Models F-18???
I've got one of their F-16s still in the box, and it would be virtually impossible to get it to fly DF or turbine it is almos solid foam, and it's too small.
Increadible out side the box thinking when they designed it and it gives scale like results.
You'd spend a lot less time and money on a designed for DF/turbine mode.
HTH
Tom