A weird detail I've noticed when using Immersive First Person camera when setting myself to 60% height - when I crouch-walking into a 1-block hole, my camera seems to get stuck on the entrance to the hole. My camera stays in place, I see my arms continue forward into the hole, and then when they reach the other side my camera snaps into the correct place on the other side of the hole. When NOT using the Immersive First Person camera, I get the expected behavior of 60% height, which that I crouch-walk through the 1-block hole and my camera stays 'where my body/head is'.