What I did Friday night was mount some L-brackets onto the bottom of the frame so that the magnets would grip.
With some luck, the brackets are not in the way when the electronics tray is folded down!
One problem I ran into is vertical alignment....while the magnets hold the access panel in place, there is some vertical movement. If I had the power coupler installed in the access panel, it would probably solve this issue. However, I misplaced my power coupler faceplate, so I can not put that in.
As a short term fix, I bolted in a small metal to act as a tab.
Now the rear access panel goes on and here's how it looks...
