the copper acts as a heat sink, allowing you turn the amps up and get good penetration on relatively thin material, and keeps the puddle from dropping out the bottom. Though stick welding thin material is still going to be an ass ache. As i said before known about them for years even have some copper laying around just in case... never think about it until after I fill all the holes I just made.
If you have a few exter bucks consider getting a mig set up, probably around 600 for a mid grade homeowner model and a bottle, maybe a little more if you go all out and get upper end stuff. Not as powerful as a proper stick machine, but nice clean welds for the average do it yerself back yard hack like myself. Plus they weld out of position very well without all the bothersome technique you need with a stick welder... well most of it anyway... Find units all the time on C's list for reasonable prices.