As far as sliding goes, these behave like grippy suction cups. It's just a no-go. I use some nylon furniture sliders purchased at Home Despot for positioning, these are about 1/8" thick and available in many diameters- I use a 2.25" set for Gaia 1s, then remove them once optimally positioned. Works like a charm. For carpeted installations the spiked cups, really do help significantly. At least, that was my experience. Hope this helps.
Isoacoustics Gaia Speaker Footers
Replacing the spikes in my Soundocity outriggers (Soundocity made me a set of outriggers with threaded holes) with the Isoacoustics Gaia 2 footers has improved the sound of my Merlin VSM speakers. They now sound more open and articulate than with any combination of Z-feet or other spikes, with or without outriggers, on the floor or on a platform, that I've tried. Like the Townshend products the Gaia footers completely decouple the speakers from the floor, allowing them to float. See:
http://www.audiostream.com/content/isoacoustics-gaia-isolation-pucks#IVXH8EtVAjQdwbuj.97
http://www.isoacoustics.com/products/gaia-series/gaia-i/
http://www.audiostream.com/content/isoacoustics-gaia-isolation-pucks#IVXH8EtVAjQdwbuj.97
http://www.isoacoustics.com/products/gaia-series/gaia-i/