Shorten your backswing.
 

The one thing that helped me with hitting was to shorten my backswing.Once you get the right arm driving correctly if you shorten your backswing as much as you can it makes a massive difference.There is actually an increase in power if you can believe it.

That's why extensor action is so important, if you have it then that will limit your backswing to the point to where it "needs to go" and not further