Can't render head shadow

Godot Version

v4.4.1

Question

Hi, I have a first person character with an attached camera. I also have a light in my scene which is set to cast shadows.
I am getting a working shadow on the ground but I cannot get the shadow for the char’s head. I figured it’s because the head mesh is hidden on the camera layer, however it is visible in a different (debug) layer.

The light has access to that layer as its Cull Mask. So if I got the gist correctly I should be able to get what’s on that layer from the Cull Mask and render it on a Caster Mask layer visible to the camera. So in theory if I have an object on layer X, hidden to the camera, I can get the shadow from that layer X and re-point it to a layer Y visible to the camera.

What am I missing?