I would also check the smoothness of TrackIR. I had mine set on 50 with TrackIR5 and pro clip but dropped the speed to 0.4 and the smoothness to 23.
I no longer have to look way away for it to move out of the "dead zone". I turn my head to my 2 o'clock and can see everything behind me. Little more of a sensative setup with very slow little head movements so i can see my surroundings.
Ralfidude on Youtube has a very good video as well.