| After I did my hatch area, I learned that this type of material is designed to primarily reduce panel vibrations. It is much less effective at preventing sound wave transmission and/or sound absorption. Like you, I did the complete hatch area. However, after some research on this topic, it was obvious that I could have used a quarter of the material and would have achieved the same results. For example, to prevent speaker vibrations in the door panel, you only need a couple of patchs about 6"x12" mounted centrally on the inside to prevent resonant vibrations. 
I ended up using two types of high density closed cell foam pads that had a solid membrane on one side for the balance of the interior on the rest of the car. The solid membrane block the sound waves, and the high density foam absorbs it. Dynamat, B-Quiet, Brownbread, etc, are much less effective at absorbing sound. Plus it can begin to add a lot of weight. The good news is, its weight over the rear wheels. If on the other hand, your objective is too add 1000 watts of speakers in the hatch... then you are on the right track. But seriously, if you are interested in sound proofing the whole car, think about using alternative materials which are better suited to this end.
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