tinknocker,
There is another option out there that you might be familiar with. Blowpipe folks use an arc welder, a carbon rod (AirArc) and silicon bronze welding rod to join sections of blowpipe.
When you strike an arc, the carbon rod turn white hot and you use it for the heat source to melt the bronze rod. It does this pretty fast and the heat is contained to the immediate area. I could see a person tacking panels, but don't think it would work well to run a continuous bead. Just another (strange) idea!
Stuart
