Has anyone ever heard or used a silver tin type material to use as a port? The place that built my box used a round port, and they had to curve it inside the box becuz the port had to be 20". But they used that aluminium type material....and within 1 day of using my subwoofer, the material broke a part, like little slits in it formed at like 3 or 4 different points. I would have thought they would use PVC pipe or MDF.... any ideas?