bass affected by stand filler level?

Fill them suckers to the top! :)

The true answer is that there is not such thing as "over-damping" a speaker stand... the mass is needed to transfer to floor or subfloor that can reproduce beyond the actual range of the speaker.

High mass and NO decoupling is the best for speakers. Don't believe the marketing crap... firm coupling is the only rule with loudspeaker enclosures.

The coupling or uncoupling issue is as yet unresolved. I am getting a pair of the new Townsend speaker cradles which uncouple the speakers. Presently, I couple the speakers to wooden floors using special tiptoes from the US importer of Acapella and have IsoClean pucks under them. I have heard the decoupling is far superior. I also heard the improvement when Beauhorn came out with a base that decoupled the Virtuoso speakers.

But since you are going with a coupling, I would say that mass over a very small surface, such as with tiptoes would be best. I would therefore fill the stands. I would also suggest that lead shot would be far superior.

Well, I will give a scenario of opposite proportions.. I have used Granite and Sand loading on top of speakers in the past... Granite really thinned out and added some extra level of precise flattened soundstage... Bass was actually a tiny bit tigher, but lost some of the in room feel, so if you want a little more natural impact, than granite on top OR under the speaker was not the best musical sound in my opinion.. Accurate yes maybe, but totally enjoyable no..

Sand however on the top had a similar effect, however to not such a degree... Now that being said fact is if you don't fill the stands, than you may not have as clear of strength in the midrange and highs of the speaker due to loss of mass, however lets say you fill the stand halfway and give up some of the mass you might experience a Fuller more wooly bass sound, so yes you could take the bass to the point of extreme tightness and possibly suffocate that vibration sense if you want more of that.. this is just in theory of what I have mostly experienced, its gonna take a pain in the A$$ of some experimenting trying it both ways dumping and adding sand..

Maybe a Mix of sand filled in by some Lead shot to up the mass and not dampen the speaker stand so much could be a good option too.. Just put in the 5 or 10 pounds of shot and then pour sand over it to filter in between, and just add a little at a time or something and see what kind of tuning you find.

Not a good "opposite proportion" at all. The less filler, the more open area you have to resonate and the thin walls do not have attached mass and turn the area into a resonator. REMEMBER: thin & light material + rigid + vibration = a classic transducer. Just research NXT for more info on this. You cannot "tune" a speaker stand. It either creates undesired resonance due to lack of mass... or it is silent. The only way it could sonically "help" to have a hollow or partially hollow tube underneath a BIG vibrating mass (called a speaker) if is you actually ENJOY distortion and a steel tube trying to reproduce frequencies... but there is no in-between. I personally do not want a steel tube or other non-damped material to attempt to "reproduce" frequencies other than my loudspeaker :) You will get lower bass response by moving the vibrations to the floor, where the sheer size is able to help reproduce low end extension. Worst case is the floor won't resonate and you will just get the actual loudspeaker reproduction response... both a win-win.

Audiavreseller, sounds good in theory, but all floors do resonate. If you live on a concrete slab as is typical construction here, your speakers will be shaken by the trains going by. Mainly I find that concentrating the speakers mass on a fine point sounds best, but with my Beauhorns, their gel base improved the sound. On my Acapella LaCampanells, I am awaiting the new Townsend speaker craddles which decouple the speakers. I am told they do magic.