Mye Speaker Stand type of fill material

There is another damping material called "Black Gold" made by Lovan. It's not too expensive, maybe you want to give that a try??

I used steel blasting shot and sand. Very inexpensive.

That is good news. I am a Star Sound dealer and have had some on order for quite a while.

I am using and am happy with the Star Sound Micro Bearings from Star Sound. Via phone he was able to calculate the amount I needed. It was less than I was going to order. He also uses flat rate shipping when possible so my shipping costs was $13.00. I believe it would be worth a call to Star Sound to discuss your situation.
Good Listening.
David Pritchard

I am doing something similar and was going to use Micro bearings from Star Sound but they are temporarily unavailable. I used Atabits, which are small steel shot which are imported by May Audio. Their sourcing was changing from Atacama to Target so they too may be hard to find. I would like to say that I had conducted long listening tests of every available material but the truth is I wasn't happy with lead, sand, or kitty litter so was looking for something else. Happy so far but not had enough time for definite conclusions. The shipping on either of these will be fairly high as they are quite heavy.