This is my first comment in audígon.
I’m an engineer working for over 20 year on dynamic analysis and vibrations. Normally in airplane components.
Like pretty much anything in relation to stereo systems, there are more that one possible argument or interpretation. There is no specific data all the discussion are based on assumptions.
the wood block is made of hard material and at the same time the large weight and high stiffeners produce a low resonance frequency where music vibration has low influence in the block but given the large mass factor of the block, it influence any other component in the vibration path.
the rubber feet had a linear dampening relation. The metal decouple feet has the differential factor of reducing the amount of energy transfer thru the system.
therefore the system final result can be very similar. If you want to reduce any vibration the best thing would be put neoprene under the metal decouple plates. but High dampening materials have limitations depending of the mass load and displacement amplitude of the vibrations.
you need more energy to move a heavy component. If you reduce the amount of energy input by the decouple support…. The system is more stable.
the sand only benefit ( in relation to speaker stands) is the high mass and
Moving the cg of any system to a lower point, making the stand more stable.
like I said in the beginning there is no simple answer.
every system is different and it depends highly of everything around.
if you are not happy with you system or sound I don’t think those changes would be a game changing…