I have used Dmat for years on restorations but have disco'd for reasons that over time the product drys out and cracks, losing it's sound deadening properties.
When I discovered it had failed on a VW I did some years back, very disappointed, and worse, it is real hard to scrape off brittle crap. Done with Dmat!
Second Skin was recommended to me, it has a different chemical makeup and does not dry out.
I personally have needed it at this point, many things to do before hand on my '80, so will be giving it a try soon.
FWIW