A-body armrest - stripped threads in door’s sheet metal

The screws go in at a steep angle up.

View attachment 1716243633

The sheet metal is basically vertical. The rivinut would be basically vertical.

Won't work.
maybe the best case scenario is a conglomeration of ideas.

Cut a slot above and below.

Rivnut.

Put a bolt in rivnut and twist to the angle.

Mig up the slots and BAM!