Tried another mouthpiece, don't remember which one, still not comfortable.
Had to clamp down when I turned my head with the rubber hose.
Put a flex hose on my primary, problem solved.
Was going to a swivel if that didn't work, but happy so far.
FWIW my fixed 70-degree swivel doesn't do anything for turning the head. Maybe an omni would work, but I think the plane in which I turn my head is not the plane in which a swivel swivels.