That doesn't happen to me. When I look back with the hat my head position is where I put it, it doesn't recenter.
Hmm... Ok, I'll try to describe it.
We all know without trackIR, you can save your head to different positions for different views, right? So for example, when you don't have any button pressed, you have your head centered in a neutral position behind the gunsight. However with planes like the F6F, when you hit back on the hat, you can put your head up as far forward and high as you can get it so you can see out the back as much as possible, so when you hit back on the hat, the location of your head moves there, right?
When TrackIR is enabled with X, Y, and Z, when you hit back on the hat, it doesn't use that forward and up location for the center, it simply turns the view back from whatever your center location is for your trackIR. If it's still unclear I'll try to get some screenies later.
Wiley.