Just speaking as somebody who has maintained my share of aircraft with that
lousy Cessna-crafted fiberglass (itchy, heavy) insulation, you are aware that
the double-faced aluminum foil with a bubble sandwich is available, aren't you?
That it is half the weight and doesn't waterlog like the fiberglass? That you
can cut it with scissors and shape it in place? That it is relatively cheap and
does a hell of a job on soundproofing?

Jim
Jim Weir (A&P/IA, CFI, & other good alphabet soup)
VP Eng RST Pres. Cyberchapter EAA Tech. Counselor
http://www.rst-engr.com