Years ago while researching this myself, I stumbled across an article documenting the use of an anti-resonation, self-adhesive mat combined with a double foil-sided, non-flammable jute-type mat that was sealed with aluminum duct tape along the seams and edges to very effectively quiet, insulate and seal off the cabins of aircraft.
The main focus was to illustrate that strips of a Dynamat type self adhesive was used to dampen panel vibrations just as effectively as covering large areas. I buy the Dynamat Extreme Bulk Packs on sale and only when there is free shipping, because it is heavy.
The "heavy-lifting" of actually rejecting sound, fumes and heat transfer from passing into the cabin is done by laying out a continuous layer of double foil-sided jute type mat. The trick is to cut the mat into a pattern, much like a tailor does for clothes. Then all the seams and edges are sealed together with that wax paper covered, aluminum duct tape. The entire blanket can be removed in one-piece if needed after releasing the edge tape, and it retains the shape of the interior while on the ground.
On my '70 E-Body hardtop, I covered the interior from the bottom of the front windshield to the bottom of the rear window and from door sill to door sill. I also installed it under my headliner and behind both door panels.
The car sounds like you are in a vault when the door closes. It's actually stunning, and quieter than any of the high end luxury cars I have sat in.
My A-Body is a convertible, but it is still covered from the bottom of the front windshield to the top of the rear seat. It makes a noticeable difference in that car too. Be mindful of covering areas where moisture puddles. I leave an opening in the foil mat over the rear footwells for instance.
