wurth sells nice 10x22 sheets of sound deadening panels that are heavy duty bitumen based material with a polypropylen covering. seen it on oem roof panels of benz or audi etc. Stuff is real nice quality and i think it has more
stiffening properties than dynamat. In some cases of ex vinyl roof cars that were weakened by pitting or corrosion that stuff would really help.
Used it on both of my builds very happy with that product.
here is sample link, though i ordred direct from wurth rep.
http://www.goodspeedmotoring.com/wur...ng-panels.html