If you want to weld stainless steel to copper for a sculpture or art piece, a good option would be to use silicon bronze as your filler. When working with super thin material like this use your foot pedal to control your heat and just keep enough to melt the metal and back out if you need to if you blow a big hole. Watch the full episode welding dissimilar metals on YouTube https://youtu.be/sb19GhBFjhk | Weld.com