Did you read THIS
I used spray adhesive to attach the MLV to the inside of the engine cover. My MLV was more like 1/2" thick. I left the MLV shy of the edge of the engine cover to allow the factory insulation to fit under the gasket. Then I sort of forced the factory fiberglass/foil insulation back into place and tucked it back under the rubber gasket. I had to trim off some excess fiberglass in a couple of places.
I think the diesels may have more insulation from the factory than my gasoline model, it may not be possible to put 1" additional in there. It does seem quiter. the biggest improvement was making sure the rubber gasket was sealed to the floor all around. The gasket is designed to trap the floor mat/carpet as well. If the carpet isn't under the gasket noise can leak through.
I haven't driven on rough roads and checked to see if it has fallen off or melted yet.