>>289614201
Brainlet here with no experience in unity physics. Can you make a new ball object inside of the player object with the same controls as HMD position but locked on Z axis to where the feet would be? Then when new ball collision wants to move things higher you move the whole player object so the ball and camera are moved. Either way I would focus on getting the ball to move with the HMD before worrying about making colliders affect everything else.