Would you let someone slap you in the face repeatedly during sex? Now I would be lying if I said that parts of my body don't mind being hit during sex, but this dude looks like he is trying to knock ole boy into another video. I'm not really big on pain though, or surprises so this is something we would have to discuss before you did it.
"yeah i like to smack the shit out of dudes while I'm fucking them"
"oh, ok, well lets just see if we connect"
But if you just smack me in the face out of the blue, I'd probably still be ok if you hitting right.
Of course we have a video as an example.