Here's what I did for my electric Fiero. Coroplast with plastic bars for support so I didn't have to use 100 screws. Joined two sheets using plastic "H" channel made to connect fiberglass wall panels. It was a little tight so I had to use a heat gun to open up the "H" channel. Or maybe it's an "I" channel
OK that didn't work since I'm a noob and can't post links or pics.
Let me try this, copy and paste, I promise it's not pr0n
i550.photobucket.com/albums/ii419/JRP3_photos/DSC00976.jpg
i550.photobucket.com/albums/ii419/JRP3_photos/DSC00977.jpg