I can't compete with LJ but did once have a go at the 810 kts at 11,000 ft in an A-fit FG1 (no tanks). I got it slightly wrong and ended up with 825 kts at 15,000. It was interesting to say the least, mainly because I hadn't given any thought to how I was going to slow down. I decided to try a gentle reduction to min burner for starters. Good decision, because even that produced a deceleration akin to taking a cable! Didn't try it again...