I have now figured out that I am totally missing the shell covering and that the base mount is broken and missing some of itself. I will try to upload the diagram I was finally able to locate. I have ordered in a new shell and a new mount.

The mount is held on with two screws which are covered by the parcel shelf. I thought of removing the parcel shelf but this is a lengthy process, open to opening new cans of worms. So I have decided to cut away the shelf or to drill through it to get at the screws. I can find some kind of blanking plug to fill the holes when finished. I began with cutting but then discovered the screws are further forward than I had thought so I am now on the brink of drilling two holes through the parcel shelf material.

I will try to get some better diagrams and pictures up in my next post. The image offered up here is not a particularly good one.