Use the copper trick, it will stop you blowing through, but this puts the advantages of the portamig to the front, when your welding two pieces of metal with a gap, even 30 amps can be to much, with the portamig on the second lowest setting I can weld along the edge without it burning through, that setting would be to low if I was doing a lap joint, it's handy to fill the holes that you get from deep rust pits, the thin bit burns through, but you weld around the outside of the pit to the centre