I have only been playing a short while, I am 58 years old, and not very big, but on the odd occasion I drive the ball correctly I can hit about 210 yards. Baring in mind this has been in January with the cold air and no run what so ever, this would equate to about 240/250 yards in the summer. This I do with a 15 year old Callaway Great Big Bertha which cost £4.50 on ebay.
Firstly, your already driving a reasonable distance, secondly, if you are really desperate for a few more yards I would spend your money on a few lessons.
Firstly, your already driving a reasonable distance, secondly, if you are really desperate for a few more yards I would spend your money on a few lessons.