Lee,
I have the ARC version with a ST 90 and Pitts on it, and it is perfect. Plenty of speed.

A few things to think about:
1. I definitely agree with the dual aileron servo idea; torque rods are not good enough. You will find yourself wanting more aileron pretty quickly.
2. I have a buddy with a Magnum 1.20 four stroke, and for some reason it just doesn't have near the speed that mine does. However, his is pretty new and I don't think that he has got the best prop for it yet.
3. I had to add some tail weight until I moved the servos to the tail, then it was perfect.
4. Make sure the LG is secured very well.
5. Definitely make sure the Firewall is pinned, glasses, etc. It is a pretty heavy plane for its size, but it lands slow and takes off in a heartbeat.

Here is a picture of mine. The canopy was shot off by an evil Nazi on its most recent flight . . .