I used some flat aluminum and took the cup holder apart and used a screw through the bottom and drilled a hole in the flat aluminum. Then I lined up the dog leg of the aluminum and drilled the holes through the aluminum, the plastic cover into the bulkhead. Then I used a self-tapping screw to attach it to the bulkhead.

If you go this way make sure all the parts are there when you purchase one. I came across a lot that was missing pieces and the rubber at the bottom of the cup holder was cracked.

Nelson