Regarding having the sticky stuff coming unstuck, it can happen.  It is imperative that you apply the material to a scrupulously cleaned surface.  Scrape (if you've pulled fiberglass insulation), then sand to roughen, use a tack cloth to remove dust and wipe with a cleaner like MEK or thinner.  You want it clean to promote adhesion. Use a small roller to help press the stuff against the metal surface and you want to do this at a moderate ambient temp, like 60-80F.  As in painting, prep is everything. 
I also used foil tape (real metal tape with adhesive, not duct tape) to seal the joints where any of the black gooey stuff could leak through onto things you'd rather remain un-gooed.  I did this after getting some of the goo on the mattress cover.
Stephen 

     On Thursday, August 6, 2015 1:32 PM, Stephen Grisanti <bike2vcu@yahoo.com> wrote:
   

 Quick Roof is one name and can be purchased at home improvement stores.  We have both Lowe's and Home Depot locally and I forget at which I made my purchase.  This was done after ran out of B-Quiet, a sound deadening material that is indistinguishable in appearance and perceived effect from the official stuff.  The generic stuff runs about half the cost of the other, even before you begin to figure in the freight. May be found under other names like Peel and Seal.  

     On Thursday, August 6, 2015 1:08 PM, Pat Spragge/RFAN <Pat.Spragge@RFAN.COM> wrote:
   

 Does there seem to be a consensus that these products actually work?  Or 
is it largely marketing?

Patrick Spragge

From:  Stuart MacMillan <stuartmacm@GMAIL.COM>
To:    vanagon@GERRY.VANAGON.COM, 
Date:  08/06/2015 09:32 AM
Subject:        Re: source for peel-n-stick sound deadening
Sent by:        Vanagon Mailing List <vanagon@gerry.vanagon.com>

I like Fat Mat Rattle Trap Extreme.  Go Westy sells it, but you can get it 
direct for less:  www.fatmat.com  it sticks well and is designed for 
rattle traps like ours.  It's available in various quantities and kits.

Stuart

-----Original Message-----
From: Vanagon Mailing List [mailto:vanagon@gerry.vanagon.com] On Behalf Of 
Karl Wolz
Sent: Thursday, August 06, 2015 9:15 AM
To: vanagon@GERRY.VANAGON.COM
Subject: source for peel-n-stick sound deadening

This subject has been brought up a few times.  I thought someone mentioned 
a product from Home Depot, but I couldn’t find anything there.  Thoughts?

Thank you,

Karl Wolz=