concave and collision models have to be convex
???
Its a simple thing to make a collisionmodel for this prop.
I'll show you a working CM that WILL work ingame:
all sides just have to have the same smoothing group (1) and the same "material ID", and the same texture as the model it is posing for.

My HUD along with all my other textures have been recuded in quality.
about that btw:
put this line
"$ignorez" 1
in every hud-texture vmt :)