Re: Welding a rollcage
I believe that MIG Welding will have enough penetration if enough amperage is used.
If you have a question about the penetration take a couple of short piece of the material, you used to weld the cage with, and weld them using the same method and settings. After they cool cut the pipe in half and see how far the penetration is.
Also, NASCAR requires TIG welding of cages and frames, mainly for heat contol on the metal.