25% according to this website. My anecdotal experience with my previous '73 bay agrees. See:

http://sounddeadenershowdown.com/

And in particular:

http://sounddeadenershowdown.com/wp/treatments/techniques/installing-a-cld-tile/

-Jarrett
89 Westy (sound deadening in process)

On Oct 24, 2012, at 3:08 PM, Marc Perdue wrote:

> Does
> anybody know whether it matters if you try to cover all the metal or can
> you just cover a large portion and be done with it?