I tend to hit a high ball with a driver, so tried a Mizuno MX600 with a Prolaunch Red stiff at a recent demo day.
When it went..it went miles, but I felt like I got no help at all from the shaft. It was *very* stiff and I had to really work at turning my hands over, just to keep it from slicing!
At an even more recent Ping demo day, I tried the same shaft in a Ping G10 and whilst a bit more forgiving than the MX600 (down to the head I suspect), it was still a bit of a beast to keep straight.
I suspect you need to consistent 105+ mph driver swing to get the best out of it