I've used TrackIR5 for quite sometime.
I don't believe dead zones are necessary for all those talking about neck strain. I think people are actually creating an issue where there isn't one. Real life is my basis.
When you are in a car, bike, plane or vehicle of choice, your view is NEVER fully centered at some imaginary perfectly calculated center point. Aside from your head moving to some degree constantly, even when still it is never centered perfectly. I think most people here are forcing themselves to create this mathematically perfect center point that they need to keep their head in.
Now, although TrackIR has a center point for the game, there is absolutely no reason IMO for the need to "force" or physically constrain your head at that point. Just play the game and keep your head where you want it, like in real life.
That being said, I do have Voice Attack set to "center" the TrackIR view by saying "center" during the game. It sometimes helps readjust where I want the center to be if it seems to be off due to movement of my headset which the clip is attached to.