I've gone gongy

[steamin10]

The simplest (and cheepest) way to form this thing is with some creative hammer work and a sandbag. Get a coupla cloth potatoe or onion sacks, the fine burlap type, and triple them up and put any kind of fine sand in them and close it up. When on the floor your bag should be about 2/3 full lenth and about 2-3 inches thick. Getout some 1.5 to 3lb sledges, and some assorted ball peen hammers.
Start by gently whacking two or three inches from center and spiral out, About an inch from the edge draw a line around to guide the lip rolling. whack with a ball peen , first on the line and then next to it on the soft sand and everything will shape up . For the final round edge bend I would make a hammer head faced with a 5/8 or 3/4 rod that is bent to a shorter radious than you are working, to finish the edge roll. All the time working around on the sand bag.
The sand bag is to prevent gouges and scratch marks on the piece , and to provide a changable shape that yeilds to the hammer under your piece.
All your hammers should have their faces smoothed and polished, so any rough work with them will not be left to mar the newer surface to be worked.
The final form will be a flattened Frisbe shape, much like a stainless pot lid. The tone will be what the thickness, size, shape and stress will allow.
Many grades of stainless are prone to cracking. So workhardening may be at play. you'll have to go by sense and feel and maybe anneal with a torch.
This method of forming is done on many hand made objects. I have used it with great success for the old 70's cars that had rot spots everywhere. Now they use frp compounds or just replace. No Craftsmanship anymore. In body work a soft leather bag filled with lead shot was a good former, but for big stuff a sandbag worked.