I was fit for my 910D2 two years ago and am concerned that it may be time for a shaft change. At the time I was fit for the Kai Li R flex but was right on the border between R and S with a 96mph swing speed. I hit both the R and S flexes and chose the R flex due to my average loading at the transition (at the time). Now, I'm concerned the shaft feels to light and whippy and I can't go after the ball like I want to as a result. I have really been struggling with timing and it seems I loose the feel of the clubhead and shaft when loading (now more aggressively). What are other clues that it may be time to go in for a refit?
I would definitely go in for a new fitting. Shafts do tend to wear out overtime from excessive use, and it sounds like yours may have. The guys can fix you up in no time, and you'll be back out on the course with more confidence.