Stick down sound proofing ,Insulation?

I used FatMat in my Duster and my Dart. The stuff you buy at the hardware store isn’t intended for automotive use. Yeah sure it might work ok in some instances, but it’s cheaper for a reason.

You can get enough FatMat to do the whole floor of a car for $150, so it’s a good savings over dynamat while still being for automotive use. They even include a dynamat sample for comparison. And it does peel up later if you need to remove it for some reason. I even used it on the underside of my roof, it’s stayed put upside down on 110* days when my car was parked outside.
FatMat 100 SqFt No Logo Sound Deadener For Cars & Trucks! Free Dynamat Sample | eBay