I am swinging and hitting with some old drivers, one with 54g in shaft weight and D1 and the other one 65g in shaft weight and D3, the D1 and lighter weight 54g is easier to hit and swing for me. Is this because of me not strong enough for heavier shaft? The lighter shaft will give more speed. Why is I can feel more with D1 rather than D4? and is any difference for swinging and hitting? Thanks.