I asked "our" pro filip peliwo about that.
he said he thinks that he usually hits with a slightly closed face (but is not sure because he doesn't have slow mo-we don't know if he is experiencing the closing after contact or actual contact since that happens so fast), but he is pretty sure that he doesn't hit the ball below Center. of course this is just an anecdote because he is not a scientist and many pros actually don't know what they are doing in Detail since that happens so fast and they do it intuitively since their childhood (a lot of MLB Players think they swing down to contact) but I think it's still interesting to read.
Originally Posted by fpeliwo
It's tough to say, I can't speak for myself cause I've never seen a close up slow motion of my forehand. Fed seems to hit the ball down there quite often. He does have quite a small racket head so that doesn't make it easier to tell. I definitely don't hit the ball down there though, all my shots are towards the upper beam and top of the head, so towards the far top corner. If I hit the ball that far down my frame it would be a shank. I guess it depends on the player. You have to remember Federer has a grip tilted very much towards an Eastern or even towards a Continental grip so his forehand mechanics and strike zone won't be the same as someone who uses a semi-western or western grip. As for the tilting, I don't think I hit with a completely flat racket face (Unless I hit a flat shot), it is always a bit closed on contact, but only minimally, if anything. Wouldn't be able to tell you for certain until I see a slow mo of my fh.