ORIGINAL: xanatos
I recently graduated from my trainer (also an Avistar) to an Ultra Stick 40. This was a great 2nd plane for me. It is relatively easy to fly and land as well as being able to do some decent aerobatics. Its a tail-dragger configuration and you can set it up for flaps if you wish (you might have to upgrade your radio of course). I would agree with the other guys - keep your P51 for your third plane.
Ian
I did the same thing. Ultra stick 40 is a good 2nd plane. Much easier to take off and land than a trianer. Much more stable in high winds. Very durable and light weight ARF (5 lbs with 46FX). The best part is that I have 7 planes now and I still like flying the US40. I never get tired of it. On low rates and a sport prop flies better than a trainer. Up the rates, move the CG back, add a 3D prop and you can hover all day long.