As I recall, most free flight models are set up as essentially a tandem wing plane with both the main wing and the stab having upward force. The CG can be as far back as 70% of the MAC. This works for free flight, giving pitch up and climb under power and 2 lifting surfaces under glide.

This arrangement doesn't work well for RC. The plane will be extremely sensitive to elevator and very power sensitive. RC planes normally balance from 25%-30% of the CG, with some fun fly and 3D planes farther back. The force from the stab is downward to counteract the pitch forward rotation.

I have flown several old time free flights converted to RC with elevator, rudder and throttle. If they are balanced around the main spar, they fly very well. A buddy and I have a Quaker Flash on glo that we take out every once in a while and it's an excellent flying RC conversion. It has the CG around 30% of the MAC.