Ok, the K8 covers as made by Frankenbike, mocked up on the left side:
The rear upper tab actually lined up, so I kept that.
Then I cut off the other two tabs and glued half inch magnets to them. JB Weld has steel in it, a fact I knew but did not think about when gluing them to the tabs.
The JB Weld actually crept up the sides and started to flow over the top of the magnet! Creepy, and cool at the same time.
Then I glued an angle bracket to the cover, bending it slightly so it would be parallel to the magnet for maximum contact.
I wanted to test the strength of the magnetic bond and the fitting, so I snapped it in place:
Looks pretty damn good for a first try!
The holding power of the magnets is about as good as the remaining stock cover I have, but not nearly as strong as the FB tabs.
The magnets could be considerably larger than they are now, but that was what was available at the local ACE Hardware. I will have to get them off the web or something.
I also am looking at a larger baseplate than provided by the tabs. I am thinking about some carriage bolts I saw that had 1" or larger flat disks instead of hex head. That would be an awesome platform for a larger magnet. Also, they work better when sandwiched between plates, so an anglebracket:magnet:carriage bolt sandwich would be very strong indeed.