Hum, the AMA text found here http://www.modelaircraft.org/templat...-files/538.pdf says explicitly that the model should have flaps, but does not talk about retracts.

I don't have experience with a big warbird, but is not the difficulty linked directly to their weight ? Any very heavy plane is difficult to fly safely, no matter which speed it is able of ( When I say heavy, I should say heavy wing loading, as the absolute weight don't matter much), so the criteria the AMA should insist upon is wing loading and complexity (retracts, flaps), as that is what make a jet more difficult than anything else, and the closest planes from that definition are still ducted fan !

Bernard
PS- What I mean is a light Mustang, regardless to its size, is a *****cat. Now, an heavy Mustang will want to snap on you as soon as you begin to relax a tid bit....