On Wed, 18 Sep 2013 14:55:49 -0400, Nate Nagel
wrote:

I'd be careful using the foam in closed areas of a car body - it's been
done in the past, e.g. the "roll bar" of the Porsche 914, it seemed to
actually accelerate the rust. If you do foam closed areas make sure
they are well and truly closed and that no water is going to get in
there. It can make a real difference in stiffness and noise reduction
though.

It makes no sense to me to use GS foam in a car body. It will retain
moisture if exposed and likely rust the body.

There are products intended to dampen sound and seal car bodies.

I wish I had a photo of a shingle roof I saw. Apparently the guy
intended to seal the shingles along the edges -- it lifted the shingle
edges everywhere he used it.

--
"Dumb is local...As soon as you go 15 miles away from your dumbness, you see how dumb you are." -- Sherrod Small