I used to play the proforce gold/purple shaft 75S in my very old Hawkeye pro series driver.
Also have that shaft in the first mens 3 wood I ever bought, the Callaway Warbird which I used to tee off before I bought a full sized driver. When I bought the club it was a steel shaft and later on in high school I had the ProForce put into it. Still have the club today and take it to the range from time to time.
Been hitting my 2016M2 at the range when I get a chance and I'm really liking the ball flight. The fuji60S shaft seems less predicatble than the matrix ozik in my rocketballz but thats about what I expected. It has a little more whip to it. What has been a pleasant surprise is my ball flight is down.