bill,
an 80 cf or 125 cf gas bottle is good for home use. i wouldn't go any smaller than 80 cf. a cart made for the welder will usually hold the gas cyl. too & quite safely. 75% argon/25% co2 is the best all around gas for mild low carbon steel. ( what our trucks are made of. ) i hate to disagree with the manufacturer but i think my 20 plus yrs on the job welding experience should count for something. co2 sucks! it only works well at higher tempuratures & isn't very stable at lower temps. i can't believe they reccomended it for sheetmetal. it also leaves more splatter. co2's only advantage is cost. it's cheaper. i look at your site fairly often ( it's in my favorites file ) & i know your not a "just get by" kind of guy. go with the 75/25 ar/co2 mix.
the smaller 120 volt machines like the .023, .025 solid wire best & you can weld heavier stuff with it, it will just take more passes. however for sheet metal you should try an .030 size wire by jw harris called "twenty gauge". it is designed for the smaller 120 volt welders & runs at lower heat making for less warpage. it's been discussed on this forum & hotrodders.com. good stuff!
have fun & email me any time i'll be glad to help.
robert
