ALRIGHT..... Forget about those pictures. I came up with a much better mockup.
I spend some more time with a nice clean sheet of cardboard and measured a bit more carefully, and I came up with the design I wanted.
I am going to try to cut it out with most of the panels attached to minimize the amount of welding I need to do. (I will borrow a friend's welder.)
Let me know what you think!