I was looking for a way to add a threaded fastener for machine screws to the middle of a finished panel to avoid using sheetmetal screws and having them stick out thru the floorpan. What I came up with that worked very good was a rubber well nut with a brass insert. The downside is the hole is a little larger, 1/2" for a 1/4-20 insert, but I like the idea of a neat little rubber barrel sticking thru rather than a sheet metal screw.
This particular usage is to attach a bracket I made to bolt in my lower rear seat.
P.S. The insulation you're looking at is the material I had purchased at a roofing company.