RE: CG and high speed turning radius
Paul,
You're saying to mix in a little flap with elevator? The planes are very short coupled, and while I haven't tried it myself, most guys who have tried elevator-> flaperon mixes have given them up, since the down flap usually results in a nose-down pitch. With a longer tail moment, it might work though. But short tails and big surfaces make for lighter, more durable structure and a quicker feel on elevator.