Exhaust help

[Flysocal]

So I've got hooker cast headers and welded the adapter pipe. There will be a crossover and dual mufflers. Should I weld everything up from header all the way to the muffler? Or run clamps? My thought is to weld everything so it's air tight. So I would end up with headers, one huge section (adaptor pipe, crossover, etc.) clamp to mufflers, clamp from mufflers to side dump. I will post pictures when Photobucket is back up and running