Install Givi E370N top case on BWM F800ST

The universal mounting/adapter plate that comes with the Givi E370N top case gives many options for bolt placement, but, unfortunately the rest of the hardware is inadequate to work on BMW F800ST luggage rack.

My goals for the install:

No drilling/modification of the luggage rack
Offer some amount of cushion/padding to prevent the hard case from marring the paint.
Position [...]