oooh, I can see that it will pay me to not rush in, but do some reading. Thanks joey.
there is a good article here about soundproofing. http://kereta.info/how-to-sound-proo...and-materials/ paparoo painted the inside shell of one of our performance vehicles to cut the noise. he used a black bitumen type substance. he's not answering atm but i will find out what it is. my thoughts are you can just put it on the metal itself and it will not break down or interfere with anything else. rather than trying to fill a space with a material that will break down.