UPDATE: I've since set up another reef tank, and purposefully draped colonies of green polyps on the new tuxedo urchins. If you take a 3x3" piece, and gently hold it against the top of the urchin, it will hold on to it and pull the edges around its body. This has all but stopped the tendency for the urchin to lift up frags, and it's an absolute joy to see such bright polyps wandering around the tank. Polyps that have been growing on glass are perfect because they have nice flat and clean backs and are easy to cut to shape. This is a win win, because the urchin acts like an island, preventing the polyps from spreading too far. The colony will continue to grow but only really to fill the gaps on the urchin.
I THINK I'm the first person to purposefully do this! Dress your tuxedos in green this summer folks!