Before I had the firewall of the DS done I was investigating some stuff from hot-rod/racing places. It also was a heat reflector. I can't remember the name of the product though.
The place I managed to find some in Sydney was -
Revolution Racegear
Unit 3/ 191 Parramatta Rd
Auburn, NSW, 2144
Australia Ph: (02) 9648 4044
I have not used it, as the firewall was done from the other side.
The Jaycar material comes in quite small pieces - the heaviest is remarkably heavy - filled with used Barium meal or something like that! I have some that I will try in the doors of the GS - there should be no drumming with it attached.
The stuff Brad used was bought from a company now known as Plastyne Products in Brisbane and is called "Wave-Bar 8kilo"
Why is it called 8kilo he asks?
Because it weighs 8 kgs per square metre
I can't remember the name of the company at the time that he bought it, but from memory they were "Queensland Distributors" so every chance you could get it down your way.