Alex,
Properly designed and using the right tools for the job. Sheet metal can be stronger, lighter and easier to produce a complex fabricated chassis. Team 971 mainly uses sheet metal and rivets to produce their chassis. The team uses a variety of materials to do the job. We never rule out plastics, extrusion, aluminum tube, wood, pvc, steel, etc.
Here are a couple of shots of our frame before it's put together and gives you a idea how much more you can do with sheet metal.
https://picasaweb.google.com/1045493...82013058320610