There are some experienced welding guys (e.g., MARTINSR) over at www.rodder.com/rodderrap/index.html
that might be able to give you the info you seek.
They seem to hang out in the Body Shop sub-forum, or you could set up a Take a Poll.
If there's a good sheet metal welder reading this in the Seattle area, I would sure appreciate some help setting up my little Hobart 135 Handler . . . .