Been thinking about this for the last few days as it’s not something I’ve done myself either.
The main issue is that we both want the VR headset to control where the camera is by the player physically moving and have some sort of physics applied to it at the same time without losing responsiveness.
My first thought is to not use the physics system at all.
If we assume that the players feet is always under the head (ie ignore leaning), we can raycast down from the feet and if that are not ‘on’ the ground, then move the camera’s parent down over time (simulating gravity) until the feet are ‘on’ the ground.
There are bunch of issues that you will have to deal with on top of this such as moving up/down slopes, what if the ground is above the players feet etc but this is where I would personally start if I was approaching the problem.