No, only tried the Firm flex, a bit too flexible for me.
I would go for the stiff plus if I could step on the driver swing all the time.
I don't have the time to commit to work out and stretching exercise these days. If a golfer has time to work out a little bit, that'll be the best instead of searching for a better shaft.
I know, I make the same move, just when I seemed to get used to a driver / driver shaft, I'd be looking for a change in hope for even better result.