Some my front door pockets are slightly gapped or detached at the seams so the plastic is not flush (a testament to the excellent interior quality of the 98's) so it might not work...but then again! its worth a try.
One problem with the bottles of water inside is that say it is summer, and you have the bottles in there for like a week or so. I read that if the water bottle is in the heat for a long time something happens thats bad, something about the plastic or w/e
And it will irritate the skin a tiny tiny bit after handling lots of it with bare hands. oh well.
Cover your skin with baby powder before working with fiberglas insulation. The reason usually stated is that these block your pores and help prevent the glass fibers from entering your skin and causing irritation. It appears to work well for me. Be sure and get your face and neck.
The best vibration damping product that I've ever seen is sorbothane. It's probably what is inside dynamat and similar products.
Sorbothane and sound batt insulation can do wonders with vibration and sound issues.