shelves

I just bought a SH Quadraspire Q4 EVO 4 shelf rack with glass shelves and the narrow columns (I think 19mm dia). I already also have a SH Quadraspire Q4 EVO 4 shelf rack with oak shelves and the thicker fluted columns (I think 32mm dia at the ends). Is it best in terms of SQ to use the glass...

I've recently suffered a bout of upgradeitis and need to pick some brains. Cyrus CDi and Naim Nait 5si need to be on separate shelves so..... ......Has anyone replaced the small hardish pads which keep glass shelves from direct contact with metal stands? Any advice? Any suggestions? Thanks.