Well, the F3 was RTS at 750. I remember the shock I got doing a chase down oversea, flicked the HUD from mach to IAS and saw 835 accelerating. I had no idea anything could actually go faster than RTS, nevermind lots faster.
The Sageburner F4 recordbreaker managed 784 kts, with one pilot only, stripped down and polished (and they crashed the first attempt). The F3 was pretty wheezy at altitude, but LL was awesome.