>>316198875
>>316196208
>the head bone rotation is taken from your headset but the Z axis translation is separate I think
So apparently the z-axis does matter for the IK. I just straight up 0'd it out for a quick test (I tried on the bridge of the nose, between the eyes, slightly inside of the eyes), and saying fuckit with a 0-test actually fixed most of the issues. 

Issues being head tilt lifting/lowering the torso, and feet not being planted. Sitting is still wonky where it either doesn't work, or doesn't track me for 5-8 seconds before snapping things into place, but it's better than it was.