I will only speak of my experience with dynamat. It is very heavy and does not stick well to the bottom of a surface. That is, I needed to put it on the bottom of a rear deck lid to reduce vibration and resonance. It kept peeling off over time. I used the heat gun to stick it on too. Ultimately, I had to put it on the top of the deck and then recover the deck with new carpet material. I'd rate the "improvement" marginal. Tod

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Resistance is Futile.