I've been 125mph, also on a private road of course, and i wasn't in the red zone on the rev counter. So you can get up to some pretty high speeds, without worrying about the rev limiter, providing your in a sensible gear of course! I backed down on that occasion too, as it was quite windy so the car had more to give. It wouldn't be that hard to reach the official top end of 130 i don't think and i've seen an ST, going at least 135mph on a downhill stretch of a motroway. I know they it was going that fast, as i was going about that in another car, so the ST has a lot to give i think.