I have heard the GRP Rally tires are good for high speed runs. I just got a set of them, and while I haven't run them yet compared to my Ofna belted radials the GRP seem much more firm and solid. The compound is tacky, but overall the tire is very rigid. I can see them holding up to very high speeds with little or no ballooning. I'm not sure if they are belted or not. Might just be a very solid design with lots of rubber, doesn't feel like there is much foam (if any? I got them as premounts and this is my first set). Look forward to running them in the spring, as they look to be a very durable and long-lasting tire.
I also would like to pick up a set of the Sweep EXP belted radials and try those too.