Naudet, what I found about the 190s is that you don't want to swing the nose over to the 'backside' - ie) like how the P-38s would do it. The P-38s would go straight up, reach near zero airspeed and then it would flip over purely to the pitch direction, do a back flop and then point nose down.
If you do this in a 190, it could either work, or fall into a flat spin. The recently upgraded 190s (which HT says no FM changes but defiantely feels different... weird, eh?) are a lot better, but it's still a bit too dangerous. If you feel the flat spin coming you have to turn the engine off and neutralize the yaw direction movement immediately to reduce the impact of the temporary inverted flat spin.
In a Ta152H.. well.. You'll display a nice, big "falling Cruciform" performance if you attempt a pure 90d vertical. It doesn't even flat spin. It falls straight down in that position.
What I've learned is, in the 190s you have to stall out and point nose down sideways. Head straight up, stall out, and then with about 50% throttle engaged, coax the plane with slight slight rudder kicks, so it starts falling sideways to the direction of the torque(left) - and at the same time maintain certain amount of aileron input to the opposite side(right) so the plane doesn't start to spin as it reverses.
If you do it right, it will go straight up, and then reverse direction sideways(by pure leftside yawing), nose down, and then come down. I can get the 190s down to about 50mph in the vertical and then recover safely, using this method. The real 190 gurus can get it down to 0~20mph I believe.