I made a panel out of 1/8" plywood to test with. Easy to cut and mark. It gave me the chance to try out different choices and placement of equipment. After I had everything as I wanted, I got a piece of 0.32 aluminum at a local shop and made it again just to check the top flange and fit under canopy.
In the end I had Stein cut a panel for me when he built it and he did a nice job. As I sit in the plane now while I am finishing it and getting my license, I would have make changes, but too late now!