sound deadening and fiberglass

hi,

i'm going to be building a fiberglass subwoofer enclosure in the spare tire tub of my '93 civic hatchback.  i was planning on putting down some peel n seal first.  what i want to know is do i still need to put something to protect the peel n seal (i.e. plastic, foil, etc.) before i start laying down the fiberglass or can I lay it down on the aluminum backing of the peal n seal?

thanks for any tips/advice!

yeah, it's cheaper...less than $1/sq ft.

http://www.mfmbp.com/ccp51/cgi-bin/cp-app.cgi?usr=51G7380301&rnd=7384532&rrc=N&affl=&cip=199.168.7.243&act=&aff=&pg=prod&ref=PSalum&cat=&catstr=

some people say it's as good, some people say it's good enough...for the price it's hard to argue.  from my understanding it's essentially the same thing as dynamat or can at least perform the same function.