I think it's a great idea to play with different swing weights to find the one you are most comfortable with, and hit the best. I've got one driver that is D10. It came that way for some reason. I like my irons at D4 and my driver at D6. Seems of feel better to me. A heavier shaft will increase the sw a few points. Adding a half inch to your driver will do it. So will a lighter grip. You can also add weight inside the tip of the shaft.