Higher gauge sheet metal that requires to be welded is a challenge. The goal is to keep the heat under control to avoid burn-through and warping - its a balancing act to make sure there is sufficient weld strength. Short circuit transfer MIG, pulsed MIG, TIG and pulsed TIG are the best methods to control burn-through and warping. Sheet metal fabricators are tasked with financial limits and capital expenditures. Like most manufacturing processes, welding can be a make or break function of the part being fabricated.
Direct the arc at the middle of the weld puddle. In most cases, you would keep the arc on the leading edge, where the weld puddle is thinnest, to drive the arc into the work for more penetration. However, staying back enables the puddle to insulate the base metal from the arc's full force. To prevent burn-through and warping, do not whip or weave the torch, as the more time you keep the arc in an area, the hotter it becomes. Always travel in a straight line and use the fastest travel speed possible that maintains a good bead profile.