Looks good dude. So you just used Roofing material for the membrane. That is an amazing idea. I never realized that they are basically the exact same thing.
It does the same job. With Dynamat they have kinds with a foil face which is prob good for doing the underside of the hood. But there's a site matt told me about and after reading there products the sound deadener membrane they market is just a Butyl adhesive base which is the same as many roofing and weather barrier membranes used in construction. If you do use a construction membrane just read what its made out of.
Asphalt Based= Not rated for high temp applications.
Rubber Based= Holds up better in higher temps.
Butyl Based= Tested up to 400 F, Perfect for doors
EPDM Based= Used on commercial roofs, Best IMO,thick
Like in my pix above under my amps I used a Butyl based membrane, the rest of the cargo area I used an asphalt based because I have 2 huge rolls of it and its being covered by the stock sound proofing. In the high heat with the asphalt based you might notice if you put ur hand on a cut edge the black stuff will get on your hands because it gets soft and its sticky. bad for vertical applications such as doors.
For my doors I have two rolls of peel and stick EPDM membrane used for roof seams and detailing around penetrations in roofs. The stuff is thick and made to be in direct sunlight and will not be effected by heat. Though it does have an adhesive/sticky back side its a good idea to use a primer or even a 3M spray glue for better adhesion.
The only reason I keep mentioning useing a construction membrane is cost, Dynamat and similar "car audio sound deadeners" are overpriced and marked up like 400%, where as construction membrane is sold in huge amounts every day so cost is much cheaper. Im an engineer in the construction field, mainly dealing with weather proofing designs and consulting so I get away with grabbing rolls of it off sites for "testing". lol. To test out in my car.......