Driving longer is all about club head speed PLUS your ability to finish "long".

I was clocking 104 mph and hitting consistently straight 300-310 yard shots. I obviously thought my technique was flawlwss with the driver becasue very few can hit 300. The local pro walked by one day after a particularly big drive, and said I was finishing "short". One hour, and 125.00 later he had me bombing 340 yarders!

To make a long instruction short, this "finishing long" is the releasing of the forearms that everyone talks about. At impact your forearms should not feel as though they are "controlling" the clubhead. You should almost feel as though you arent controlling the head. Envision your arms as string with the head attached to the end. At impact your forward transfer of weight should be "throwing" the string/clubhead into AND THROUGH the ball. If you attempt to keep your head perfectly still, your driver head will be rising at impact in essence transforming your 9.5 degree into a 14 degree driver. Instead, you need to be driving through your target at impact (allowing the loft of the driver provide all the lifting).