This. If you're curios about how much strength proper sheet metal flanging and bending can have, make a simple square out of cardboard, and try to bend or twist it. Then take a sheet of the same cardboard, and "flange" the edges (you might need a bit of tape to get to stay...). Try the same amount of bending and twisting, and you'll notice a large amount of extra rigidity. Even more so if you can stay away from rectangles and stick to triangles.

Looks like a good start, but you might want to take it easy on the cheese holing until your design is structurally sound...