I've recently purchased a 915 D3 driver and 915F. I was fitted with X-flex Diamana D+white shafts in both. I'm pretty happy with the fairway wood but the driver shaft feels a little soft in the tip. My old driver was a 907D2 with a Grafalloy blue S-flex shaft, which played stiffer than the D+white. Any ideas as to what new shaft will play most like that old Grafalloy Blue?