It doesn’t really make sense in most cases BTW, with the exception of racing games and flight sims. In almost all other games there is no such thing as a center direction.
The headtracking isn`t correct, if the camera position (y-axis) and head position don’t match.
But it’s not a big problem, I just position the camera with the mouse until it feels right.
-Something that is a bit off topic.
I noticed that the fov gets reset every time you die or a new area is loaded in bioshock and the fov key loses its function after a while. It´s not a big deal, but you could add that to the game optimizer description.