I can tell you what NOT to use. Any of those sticky asphalt type sound deadeners that have a peel and stick side to them.
Gravity eventually overcomes them and they fall.
I prefer the really cheap, light weight fiber mats with foil on 1 side. The kind like what they put under house carpet. Places like JC Whitney sell it in huge rolled up sheets for peanuts.
Just spray the crap out of them with 3M upholstery spray glue and they work great.
2012 Mustang Boss 302 #1918, Competition Orange. FGF replacement 2006 Mustang V6 Pony, Vista Blue. Factory ordered. 2019 BMW X3 (Titled to the wife, but I'm always driving it for her. So I'm claiming it) Old projects, gone but not forgotten: 1967 FB 400, original CA car. After 22 years of work, trashed by the guy who was supposed to paint it. I had to sell it. 1980 Turbo Trans Am 1970 Mustang fastback, 351C 4Bbl, auto 1988 Mustang GT, 5 speed 1983 F-150 4x4, built 302 1994 Chevy K2500 HD 4x4, 454 TBI
It's cardboard. I used 1/8" neoprene sheeting (ebay) and 3M's Super Trim Adhesive. Leftover neoprene comes in handy for other things as well. It's what they make wetsuits out of.
