Originally Posted by woody
Well, they are mainly GRP (closely modeled on the Lotus Esprit) with a skin of stainless steel bonded over it, that's why they ended up so heavy! Stainless isn't really that difficult to weld either, you can TIG or MIG it just like mild steel, but bonding is cheaper like you say.
Mig or Tig work ok...just point out some Mig or Tig welding on the body of a car...
Pretty much all car bodies are Resistance welded (spot welded). Spot welding Stainless steel is very tricky and usually has pretty dire results. The currents you have to use to get a satisfactory weld, (4* square root of the Governing metal thickness) are so high that the electric bill from 2 months of production would cost more than a years worth of adhesive.
Incidentally, I'm a weld consultant, mainly to the automotive industry.