OK so a kind gentleman who's daughter I teach supplied me with some nice granite plinths to put the ProAc 140's on. Trouble is they are very well polished and I am worried that the speakers may skid off them. So any recommendations for little cone type thingys that the spikes can sit in and rest on the surface of the granite? I'm sure I've seen things like this used for rotecting wooden floors from rack spikes but thought I'd ask here anyway. Cheers Steve