Finding neck pivot point?

I'm trying to find the pivot point of the neck using the Oculus Rift.

http://i.imgur.com/oi36szx.jpg

Not really sure how to tackle this so right now I have...

• the "default position" when the user resets with their head in the normal position


• the "edge position" when the user presses a button after tilting their head all the way to the side


• the "head distance" which is Vector3.Distance'd between the default position and edge position


• a "head sphere" that transform.localScale's up according to the head distance (but doesn't scale correctly?)

Ultimately, I'm trying to find the neck pivot point so I can have a "shoulder point" relative to the neck. The shoulder will be used for the person "manually" aiming down the scope of a sniper rifle. At the moment, the rifle follows the user's "RightEyeAnchor". It's extremely disorientating when you want to look up and away from your rifle, but it still follows you. The idea is that the rifle's butt will be fixed against the shoulder point.

Anyone have any advice? Am I approaching this in a too complicated way?