100 percent wrong!!! Wawrinka - Eastern Almagro - Eastern Dimitrov - Eastern Federer -Eastern Youzhny Eastern. Henin and Guga use a more extreme grip.
I never said they didn't use Eastern! So I was 100% right. Thanks!
There are different
variations of pure Eastern (knuckle on top) depending on the position of the
heel pad of the palm.
The "classic"/"textbook" Eastern has the heelpad on the top bevel. This creates the "steak knife" or "pistol" grip.
The Eastern that pros use (including Federer) puts the heelpad somewhere on bevel 8 or even closer to 7, which is more
behind the handle. This makes the grip play "extreme" even though the index knuckle is in the same spot. This is called a "hammer" grip by some.
Try this: Put on a normal Eastern grip. Now roll the heel of your palm down (behind the handle) as far as it can go while keeping your index knuckle on top. This will make your all your knuckles line up on the top bevel. Now go hit some balls. It should feel pretty damn extreme, right? That's because it
is more extreme even though it is still technically called "Eastern." So I would have no qualms about calling this grip "extreme."
The heelpad is probably more important than the index knuckle in determining how extreme a grip plays. I'm pretty sure Gasquet has his heel down further than Federer.
So a player can change the nature of his Eastern grip simply by changing the heel pad and keeping the index knuckle in the same place. i.e., he can make it more "extreme" even though it is technically still "Eastern".
FYI, in the past they used to have different names for grip depending on where the heelpad was. For some reason, the system became simplified to only looking at the index knuckle. This was a bad overrsimplification.