You realise I don't care whether the claim is that it actually was 'exclusive' or not, right? You people are off in some corner somewhere having your own discussion.
If your knucks are so delicate that you can't deliver a decent closed fist, I would suggest also giving up on the palm striking, bear hugging, ball cradling or any other notion you have of "fighting" before you get yourself hurt.
Maybe take up something non-violent. Like flower aranging or male escort services.
Just mi dos centavos.
In my personal experience I have found the palm heel strike felt different, maybe it is just that I'm used to using my fist. I don't doubt it's usefulness at all in fact if you have the opportunity I'd say use it, like if the only target you got is the forehead, for some reason, go for it.
The answer to the original question is shin.
What the ****? Fine, **** it - screw this noise.
palm heels and open hand strikes are always better LEGAL-WISE in street altercations.
esp when someone claims you beat the **** out of them but your knuckles are unscathed, it goes a long way to corroborate your claim of self-defense.
& you can't just switch fists into open hands & then box. if you want to learn palm heels & open hand strikes, spend the time to learn new strikes and combinations.