I used this instead of dynamat. I would absolutely recommend it while you're already in the door panel. Whether or not you can hear a difference, you can certainly feel it every time you close the door. I used 18 sq ft for the 2 front doors and 1 rear door (left one rear door to compare), but if I were to do it again I'd start with 36 sq ft and be generous with it.
I didn't add any "soundproofing" materials, and I think road noise is one of the biggest factors for sound quality. I'm just not convinced that soundproofing is possible/worth the effort.
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View my fuel log 2015 Mirage DE 1.2 manual: 42.7 mpg (US) ... 18.1 km/L ... 5.5 L/100 km ... 51.2 mpg (Imp)