ok, so you think that dampening vibrations occurs by mass loading? huh, are you sure that mass loading doesnt just lower resonant frequency? you want to know what the real physics definition of dampening is?
Dampening This in mind dynamat is still the best material, which is a patented butyl rubber material unlike the bitumous roofing material that most bargain sound deadeners are made for. Your buddy Ant also knows that dynamat is better. He says quit a few different things, this is one before he was into making money for himself
Dynamat
Not trying to be a hardass about this but...I don't think you should defend your opinion with the wrong information. When others ask an opinion it should be your job as a person with knowledge (as you obviously have) to inform those with accurate info so that we don't continue having people filling their cars with roofing material (not talking about second skin, which i agree is a good product with good research behind it).