A lot of people have suggested that Federer should switch to a bigger head because he shanks so many balls on his backhand side. If he were to switch to a bigger sized head and he made contact with the ball the way he does when he shanks on a 90, would there be a significant difference? I doubt the ball would be all that great anyways. I think it's more due to the fact that it's a one hander at such high racquet speeds which require impeccable timing. Doubt a few sq. inches will help produce a winner.