I ordered a bunch of random pieces of copper off Metalliferous to place around and practice some techniques. Included is a 9 inch piece of 14 gauge, I had been reading about a process that forms by stretching out the middle of a piece of heavy gauge metal.
I realized at this point I couldn't get a stake in the base if I went any further, so I went ahead and rounded over the base, counter-domed the bottom, and planished the base.
After two more raisings the edge is very wavy and uneven. Since it was heavy gauge to begin with and raising compresses the metal at the edge, the metal I needed to cut through was between 12 and 13 gauge. To cut this I put on arm of a pair of aviation snips in my vise and put a metal tube on the other arm to increase the leverage. It worked rather well.
Now just clean the form up a little bit, planish the entire surface, hit it with some steel wool and high grit sandpaper, and seal the surface with wax. I was pretty happy with the way this one came out. Definitely the tallest form I've made and its the heaviest gauge copper I've tried to work with.