All of the comments confirm my personal experience. I do mix sand with the #7 or #9 lead shot for fill. However, the type of sand makes a big difference. I find that silica sand, used for sandblasting is the best. The silica sand used for this purpose must be completely free from every possible contamination, and its sharp, but odd shape packs in with the lead to form a very dense package for damping. Redkiwi is correct in stating that the results may vary. Everything done to your system that affects resonances, can go either way. It greatly depends on your environment, the audio equipment, and even the brand and design of the stand. In short, this is certainly worth experimenting with, for the potential gain to be had for such a small investment. One last thing, I suggest you get a disposable pan from an auto supply place, the type used for do it yourself oil changes. Be sure to wear a disposable mask and fill the stands (or whatever) over the disposable pan. If the tiny lead pellets spill on your floor, wether carpeted or hard, you will regret it!