If you do a search on google there are local firms that specialise in material vibration and damping agents used in structural engineering.

Check it out and contact a product manager for applications data.

I very seriously doubt acquaplas is the "only" solution to that particular issue.

With a few rare exceptions (aka M1 mid/hf driver) a compression driver was never designed for hi fidelity and nor was a horn for that matter.

But we still like to play with the First Watt.

If you want something really good consider a Scan Revelator tweeter loaded with a properly designed low profile wave guide.