I am debating doing the same thing to my trunk and doors.... to reduce noise from my system, and from my exhaust drone... Let us know how it all works out when your finished. That stuff isn't cheap.
*01 Cobra, 4.6L, P&P heads, Stage 3 comp cams, MAC LT headers, O/R Hpipe, Bassani catback exhaust, Too many bolt-ons to list..., 4.30 gears. (364 rwhp/ 330 rwtq)
*01 Roush Stage 2, 4.6L, 5 spd, BBK Bolt-ons (Wife's)
*71 Chevelle, 350, 4 spd, H/C/I, (~400 hp)
*72 C10, 350, Auto, (my Daily Driver)