photoniq,
The fact that you've soloed in the UK played a big part in my statement (in another thread) that you'd likely do okay with the Super Sportster. That and the fact that you said your instructor would be with you for the first few flights.
That same opinion would also apply to the Spacewalker. It is a reasonably stable and gentle aircraft to fly. But as I mentioned, watch the rudder on the Spacewalker, they tend to be VERY effective.
I could not, in good conscience, recommend the Chipmunk though.
Best of luck with whatever you choose.
By the way Doug and Wayne, my second plane was a Sportster, and I found it a very nice plane. Never had ANY problems transitioning to it from my trainer.
Dennis-