RE: How fast is extreme?
Well, it could be taken that way, but really it was intended as a tongue-in-cheek dig at the difference between building purpose-designed speed aircraft and overpowering sport airplanes. It IS all relative, as CP and others have inferred.
Fact is, as CP said as well, the way to up the ante is to just do it. And tell people you are doing it. Personally, I think there is a growing interest in all out speed flying, and the only way to foster that is to be part of the participant base, to "do it". And to demonstrate whenever possible what kind of performance can really be had, and on a budget too. I look forward to the time there is a bona fide F3S event (IC...) in NA somewhere.
Kudos to anyone who feels the bug and drops a 25FSR in Shrike .10, or whatever. It's all good. On the other side of that, jamming big engines in run of the mill racer lookalike GP ARF's may be good fun and all that, but it's not "extreme", and strictly personally it doesn't interest me, at least until the part where the engine rips the nose off the aircraft. But it's one way to get the rush, and this is the place to talk about it, esp. since the soft drugs often lead to the hard stuff anyway and we can only hope the addiction strikes.
It gets to the point where you get disappointed if there isn't a bit of raw terror at every launch.. but really, that's what makes your early flying exploits so exciting too. Ya just gotta keep getting stronger stuff. But seriously, it is a cool technical challenge and in the process you can learn a whole lotta stuff that can be applied elsewhere. And I've hardly scratched the surface.
MJD