I took the 190a5 all the way up to 100k. Yes, it is possible. IAS/TAS both become TAS over 55k or so, and I ran out of gas but the wind was set to full updraft so I kept going. The plane and cockpit disappears promptly at 95k, so once I turned wind off and went down it came back. I then promptly inverted, nosed straight down, trimed myself to stay there and nose dived from 95-freakin'-thousand feet! WOOOHOOO!
only.... nothing happened. I just dived. And dived. And dived. I didn't even reach creaking until 40k, and I topped out at about 630mph there, but then it slowed down... to like 590 tops (in a nose down high speed dive) in the 20k's, and below 20K I started speeding up again but only just barely touched 600mph and had light creaking.
Something's messed up if I didn't rip myself to pieces.