DON'T GUESS. Go to somewhere to try them. Indoor if possible with computer tracker stuff. That's what I did.
Ended up with Callaway X speed senior shaft, set at +2 draw when they were dumping them. Hit everything straight for 6 months. If I'd have got this driver 20 years ago..........
Although I think there is value in having a driver fitting, I think it's marginal gains (assuming the shaft being used is in the broad spectrum of acceptable shafts for your swing). I'm happy that the shaft I have is a good one for my swing speed and rhythm, and while I accept that there could be a shaft out there that is better suited, the difference will be marginal. Given my bad shot is a big block to the right caused by a swing path issue, there's not going to be much a fitting can do to help that - maybe it might be 1 yard less far into the woods?!
My view on fittings, and I respect that there are other acceptable views too, is that they help to identify characteristics of your swing that means particular types of shaft and club are better suited, e.g. shaft flex, high or low launch, but there's unlikely to be a single shaft / club combo that is scientifically the best given golfers of my ability (12 handicap under the old system) don't have a consistent enough swing for the data to be reliable enough to ever truly say what is best. So when it comes down to it, best just to have something that's in the broad range of suitable clubs and most importantly one that you really enjoy hitting - as actually the best way to improve the numbers is to practice using it until you're good at it
Not wanting to totally de-rail my own thread.... but I think there is also some good placebo value in a fitting. It takes doubt about the club you're holding out of the equation and therefore the blame for bad shots sits squarely on the shoulders of the golfer using the club.
Anyway.... I think I'll keep my eye out for some second hand bargain TM heads flooding the market post Christmas and early Jan that I could swap on to my existing shaft. I'll let you all know what I end up with!