If it is asphault based which i think it is i am not a fan of it. I would use a butyl based deadener like Dynamat Extreme or Second Skin Damplifier. They are a bit pricey but you get what you pay for. You can do a search and find threads about people with asphault based deadener falling off or giving off a nasty asphault odor for a prolonged period.
thanks guys. i'm going in with a guy on here that is local and another local guy on a big purchase of dampering materail. they wanted to go with fat mat, and i said second skin. i will pass this on to them. very helpful, thanks.