IF you were wondering .... we are struggling to precisely define the type and quantity of damping material needed.[\QUOTE]
Thanks for the update Rick. That aspect of the desigh is the "raison d' être" of the whole project and its distinctive feature, so we appreciate that getting it right and precisely reproductible for anyone that tries to build one is key.
In that vein, I think that if you could make that work with globe wide available brand products, like for example example 3M stuff, it would help a lot. It might increase cost, but that way, even if you are starting in DIY and dont have a proper measurement rig or knowledge to verify compliance, you could be sure to get the same results, and would make sourcing and applying it easier, wherever you are located.