For me, a nicely balanced pipe doesn't require any jaw pressure, it simply rests quietly between my back molars, jaw at rest. I might bite a bit if I'm working hard, splitting wood or such but, just normal activity; behind the camera, driving, doing post at the computer, etc, very little pressure is exerted through my jaw. Most bits force my jaw a bit wider than when it is at rest. So, that's the only pressure required to hold a nicely balanced pipe securely in place, just the tension of my jaw being forced open more than normal.
I think the bit/button would have to be less than an eighth of an inch thick before I'd experience a problem clenching and have to consciously "bite" down.