OK, one last "spin" on this. Since the segments are being spun why not just have a step to a smaller diameter spun onto the small end of each part that would fit into the ID of the adjacent part arond 1/4 to 3/8". This would stiffen up the edge a lot, provide auto alignment to some extent and should be simple to do during the spinning operation (as long as you do it on the small end). Since the hull shape is decorative and not a pressure vessel of any kind, you might want to consider soft solder. It would be easier to do, lots less costly, far fewer issues associated with temperature, less chance of melting a hole in something and, most important, it is far easier to undo than silver solder should the need arise. With "telescoping parts" the joint would be very strong.