I'm 53 years old 5'6' 190 lbs. 10 handicap. I have back issues and I am trying to gain club head speed through equipment. I currently hit the 910 D2 with reg flex shaft. I am interested in the 915 but am undecided between the D2 or D3. Will the smaller head of the D3 give me more club head speed or is forgiveness of the D2 more beneficial?