I’ve had the adhesive backing fall off the foam while still in the shipping bag.
It’s junk
Closed cell from any of the other sources is vastly superior.
While the engine bay can get hot, I doubt it would ever get hot enough to blister the paint. When I got my coupe there was no insulation on the hood and I drove it for a while in that condition without a problem.
I eventually did order the thicker product from classic9 (link above) and it was cut perfectly for installation. I did have some hood fitment issues and the body shop found that the thicker material was touching the air filter.
My carburetor set up is presently Weber 38's with a spacer underneath to allow the butterfly's to open fully, thus raising the air filter up about 3/4." I have since replaced the center section with the thinner material from Classic9, and will eventually pull off the manifolds and do some surgery to allow removal of the carb spacers