I believe the GS1000 cup is a single outer shell, with a wooden inner as well. So assuming they are, it would be the matching U cuts that make a hole when slipped together. It's just a significantly bigger hunk of wood to begin with. The 3B band is made by somebody Big Bill knows.
Edit: And the damping looks like Dynamat, minus the foil stuff.
the U cuts you described would be perfect, i dont trust my skills enough as for rip off the cable and try to solder it back to the drivers,
and interesting about the dynamat, thanks.