I tought my 12 year old on a P51 PTS and had no trouble. I would suggest putting the flaps on a servo and leave off the wheel "brakes". I believe it is just as stable as an LT-40, Avistar, Nexstar,Superstar, Stinger or Kadet.
The problem with the At-6 is that even though it was designed to be a trainer, the RC version is scale and won't fly like an RC trainer. That doesn't mean you won't be able to learn on it ... it'll just be a little harder.
You will get a lot of negative responses about anything that doesn't look like a classic style box looking trainer. Especially from the "set in their ways" old timers and the newbies that either found a new bandwagon to jump on or want to be just like them. There's not an ARF on the market that doesn't have their faults either in design, build, or just a really crappy hardware package. The P51 trainer is a little heavier than some of the conventional trainers, but it has a large wing area, plenty of dihedral, and flaps. The landing gear sticks out in front of the leading edge of the wing to eliminate noseovers, the wing droops reduce tip stalls, and there's plenty of room inside the plane to move things around to get your CG right (presuming the ARF version and your engine and radio). If you'll notice, most of the negative replies by people that don't like the plane are a matter of personal preference. Most don't like the landing gear, or think they should have included more hardware (ARF version), or they had trouble with the Evo engine, or the prop stinks. It's not like you have to tear it apart to fiberglass the gear block because the landing gear keeps breaking off (Kyosho Flip 3D, H9 Funtana), or it has a weak wing spar or foam wing, or there's a problem with the tail feathers falling off...
No, I don't work for Hangar 9, but I don't think it's fair for people to condemn something just because they don't like the way something looks. If you notice, most of the planes you buy have pictures of them on the outside...