I'm using Dynamat extreme, then Dynaliner on most areas. There will also be Dynapad over the Dynamat extreme in the front driver/passenger foot well area. I've been posting pictures in the Optima Batteries SEMA build (4x4 section of the forum).
I have a question about applying dynamat to ll who have done it.
What type did you use? Also can you layer different types?
Sure, the more layers = more damping, at a diminishing rate of return. It's called constrained layer damping. The sound energy in the panel is converted to heat when the damping materials wiggle the glue layers between them in shear.