Further Isolation for Spike Cups

I recently acquired a pair of Paradigm Reference Studio 100 v.2 speakers, which are placed on suspended hardwood floors. The bass and midrange response as well as sound stage improved dramatically when I removed the round brass feet and placed 1" dia. aluminum receiving cups under the spikes. I'd like to try isolating the speakers even further by attaching adhesive felt furniture pads or "magic sliders" (I think a kind of hard nylon) under the cups. I.e.:


Any sense of whether felt or "magic sliders" (or even something like rubber) would work best?


I've tried Vibrapods under Studio/60 v2 and it improved mostly bass response making it more even/musical. Perhaps it was resonating with the floor. Studio 100 is most likely too heavy, unless you put whole array of them. Vibrapods made speaker a little unstable - wobbly. My current speakers have spikes with integrated round plate underneath and react much less with the floor. Vibrapods have different weight ratings (numbers 1-5). I remember placing scale underneath front and then rear of the speaker but don't remember how many I used. I know I bought two different types. Over time Vibrapods get compressed, but you can "refresh" them by placing in the oven.
Take a look at Herbiesaudiolab.net to see what works for this type of isolation. You can even call their line to speak with Steve Herbelin, resonance guru.
Thanks for the replies. I contacted Herbies Audio Lab and the products they recommended all had hard, convex plastic undersides. I'm going to go with the "magic sliders" under the receiving cups (heck, might even sandwich the felt in the middle -- why not?, and if I like what I hear will probably upgrade to one of the Herbie's products later.