A few years ago we had an Ultravan Motorhome that had a rear engine (Corvair!!) under the bedroom floor. I got some sound material from a Canadian supplier at that time which was thin sheets of lead in various configurations....with both rigid and flexible backing and you could get various fasteners for it. I lined the engine compartment with it. That rig was almost dead silent after that....going down the highway it was like someone was towing you with a rope...no sound except road noises! It was amazing. This was so "bad" in its silence that I could not hear the engine when it produced knocking going up a steep hill, so I put a little battery powerd intercom back there! Several others in our club did the same thing. This material was kind of difficult to handle and best to keep in one piece as much as possible. However, nowadays I wonder if the use of that lead would be some kind of a hazard and even illegal!! WE also installed it in a front engine motorhome with almost the same results, but that was a "bearcat" to install. FWIW Dept. Murray Vin: 05962 Lic: DMC-XII Washington state [Non-text portions of this message have been removed]