Configure the "center" (or "reset") function to a key or button that is accessible when you are sitting back. Then sit back in your flying position, and hit this key. It will center the camera again, and consider your actual position as the center position

Think also about setting the "Pause" (enable/disable) keys, because you WILL WANT to disable FaceTrackNoIR for a small moment, when you'll have to manipulate some buttons in your VC for example.