Kb...if the original poster is smart enough to afford sim gear and smart enough to figure out how to post on forums, then he can well call Sim and order a set of pucks which were designed for his piece of gear (if he bought it used and it did not come with pucks).
Pennies will scratch the hell out of acrylic shelves...that is bad advice.
Wood, unless finished and polished, will also scratch the hell out of acrylic shelves...again, bad advice.
So I will say it again....all sim gear come with cups so the pointed feet do not damage the shelf it is placed upon. If you buy used and it does not have these pucks....CALL SIMAUDIO.