it might be kind of hard because the 21 has a slide carb (pulls and pushes) and the 12 has a rotary carb (turning) so you might have to move the throttle servo but if you can make it work that thing would fly
it might be kind of hard because the 21 has a slide carb (pulls and pushes) and the 12 has a rotary carb (turning) so you might have to move the throttle servo but if you can make it work that thing would fly