Does the ball seem to be diving out of the air? Are you getting a lot of roll out? If anything you'd want less stiffness if so. Potentially looking at a shaft that favors higher launch as well. Only way to know for sure though is to have a fitting.
I have an M3 where the standard blue tensei was not working for me. I had a broken Ozix 6 stiff shaft from my RBZ. Shaft is now 42 inches after tipping without a choice about 2.5 inches . Added 26 grams head weight. Ball flight is mid to high, straight and carrying about 230 yards with about 30 to 40 yards roll out. Happy days not to be wayward as I once was and long. Was playing off a 18 and now down to 10 and dropping.