We use foam discs from the craft store too. Seems they wear very fast if we stop them to put flies on'em. We have been useing some all-thread two nuts, two rubber cups, one on either side of the disc (probably very much like the PVC and springs) and this allows us to stop the disc for sticking bugs in it while the shaft turns. Sometimes we impale the fly to the disc and sometimes we impale a gator clip with the fly in it to the disc because sometimes certain ties or hooks become loose in the foam.
....lee s.