[fiddy6]

I've just gone through the process of setting up a mig for sheet metal work. Getting the Gas flow right helped some. Get some off cuts and setup on a bench to get it dialed in.

Make sure you are getting enough heat into the weld for penetration. You'll need a tack setting and a welding setting. I find a tack setting has high voltage and lower wire speed and my weld setting is higher wire speed and lower voltage. Gas CFM for me is anywhere between 10-15 litres per minute. I turn it up when I'm linishing the weld and there are defects in it.

I find with welding sheet metal it helps to stop and let the area cool off in short bursts. Zap and watch the colour of the surrounding metal when it gets red hold let it cool off and go again. I end up over lapping little C shaped welds. This way you can get heat in to get penetration but not too much heat that you end up blowing holes.

Practice makes perfect. Cut some scraps up and practice on the bench.