I riveted two pieces of copper together first and then I soldered the tubes to them afterward.
As far as the other ideas, There are many ideas, but most of them would actually be done much better in a machine shop. If the parts could be machined to close tolerance, then I think the light would come out great. Hand work, at least mine, is not exact enough when working on a body as small as an AA body. It would have been easier, because of the room, to do a C Maglite, but it would also be much heavier on the joint, so it's probably 6 of one half dozen of the other. Maybe some day the machinists here will step up to the plate and make something like this. I think it would sell, if it was machined for a tight fit and close tolerances.