Bob,
Flying through valleys at 420 knots is not scary.
Yes, it 'kin is!!!
I still remember one of our Leeming JP instructors (Flt Lt Pyrah?) taking me on a QFI CT ride in 1966. We found a twisty valley, THE MAN set max thrust, put both hands on the pole and went up this valley going from 80deg left to 80deg right.
Was I scared? Suffice it to say that I was concerned; I didn't like the terrain under my ass to be out of sight - I don't trust ANYONE that much.
That may be one of the many reasons I'm a truckie. The RAF was a great experience for a 23yo who thought he was pretty good - he wasn't, well, not at flying aeroplanes compared with the best.