The guys are right about making sure you're wearing your track hat correctly and setting up the sensor. When you do recenter lean just a little bit forward and also look down just a bit. With that center your resting line of sight look slightly up which means you need less head movement to get the view all the way to 90deg up. If all this doesn't help with the up view then go to your TIR profile and check your pitch axis settings.
The key is the ratio of actual head movement to the virtual head movement. If your profile is not agressive enough you may be having to look too high with your head to get the virtual head looking straight up and the sensor is losing track of the upper reflector. My pitch axis is set like this: (position:value) 0:3, 2:3, 5:19, 10:31, 20:40, 30:45, 40:50, 40:53.
Also when checking six, you'll rapidly get used to just leaning a bit to the side to see around the headrest especially if you use the centering technique of leaning slightly forward. You'll eventually find TIR is much better than the pre-set views since you can only set the pre-set to look down one side while with TIR you can shift from the right to the left easily. If you want to you can also still use your POV hat switch but it doesn't go to the position you store with F10. It'll face you directly aft and then you can shift from side to side with TIR.