I have been trying to find products to quiet the external noise ( not much there, but I want more) the generator emits. Marathon was using a egg-shell foam with a leaded material imbedded in it. They no longer us this, but I did identify the manufacturer. A 54in X 54in sheet( 27 lbs) was going to cost me $75.00 Bucks! (BTW, what is a Lew Buck?)
We don't have a sound box like country Coach or Liberty, and ever since we heard the Fisher/Panda Genset in a 2002 Millennium (which was silent) I have a aspirations of the same quiet for our Kohler/Yanmar set-up. OUr former 2002 coach got a new generator before we traded. While the genset was out, I added an additional layer of this eggshell lead foam to the walls and door. Adding more mass DID make a difference our ears could tell.