Edit: I used 1 inch angle iron, not 1/2". Also, to add to the description, I used cardboard to make the template, so I would only have to cut the sheet metal once. I picked up the 4x4 ft sheet metal at a local steel surplus center (The Yard Store) for about $12, plus a box full of used cleecos for less than $10.
"F'n" stuff up since 1990!
Some are engineers or fabricators for a living, I do it as a hobby.