Difficulties Installing ABS Headliner in 73 Swinger

I have a question on the install of the ABS headliner, also in a 73 Swinger. What are you doing to mark the holes for the sunvisors and mirror? I was thinking a thin layer of clay on the backside of the abs and make an impression of the screw holes.
Also, there is a rather large hole in the ABS where the coat hooks mount....about 1/4"