FWIW, from a guy with little welding experience, I found overlapping the metal worked better than butt welding...more metal to absorb the heat. IDIoit also mentioned that he uses a block of aluminum behind the weld to absorb the heat. Using thin wire (.023" or .024") helps too. I also stumbled across a video that said straight CO2 runs cooler than straight Ar or 75%Ar-25%CO2. I have a bottle of CO2, I should try it out. My welding has improved lots just from doing. The more you do it, the more you learn. I'm becoming more of welder and less of a grinder.