In the next three days I will be installing my permanent single 15" enclosure under the back deck sealed off from the trunk. The thing is even if I bolt it, seal it and everything else there is still that slight chance from box flex that it can still rattle with the underlying metal. I need a dampening membrane under and on top of the box to keep all quiet. There will be no carpet in the box area so I was thinking of using Herculiner on the metal then when dry using either a thin padding or a floor underlayment for the membrane then to keep it all stiff I will use another layer of herculiner over the membrane to keep in place. Any ideas would be greatly appreciated. Oh and BTW which direction is best to have the port, driver or passenger side? Polo..