no; sand or lead shot absorbs energy and deadens things. and will dampen a spongy floor. it's just not the best answer mostly and there are simply more musical passive treatments to choose from. it use to be that lowering the noise was a good trade off with less energy. but keeping things more linear mostly is better now.
Mike your post above is very welcome because as I followed this thread the question that was increasingly arising in my head was can you have too much damping and isolation and if so how do you achieve an optimum balance.
There has seemed to me to have been an implicit assumption in most if not all of the posts that the more isolation/vibration elimination the better your system would sound and that seemed at odds with other references in the past to flat sounding systems and the music lacking in energy. I also recalled Steve Williams reporting some time ago about how he had removed all the Stillpoints from his system and had preferred the resultant sound by just relying on his racks.
At the time I did wonder about trying the same but decided against it as I suspected his racks were better than mine and I wasn't unhappy with the sound of my system which has benefitted from extensive Entreq boxes and cables together with a range of Stillpoints.The Entreq is of course directed at electronic noise like EMI/RFI as opposed to mechanical noise.
As your post indicates this whole issue does appear to be more complex and chasing after ever more expensive and exotic vibration/resonance eliminating devices is a lot more nuanced than it might appear.
Have I interpreted your comments accuarately and can you enlarge and share your thoughts more fully?