[HO455]

I also installed some foil backed bubble wrap in between the stiffening ribs. This may or may not help keep it cooler or warmer, but it definitely made the WMB quieter. But not in the way your thinking.
To install the wrap I used a Gel formula contact cement. I had never used it before but I am now a big fan of it. NO runs, NO strings, NO over spray, and so easy to spread evenly. It is the best. I had no problems with it making a mess. Doing one section at a time I spread the cement with a 3" disposable brush. It was easy to lightly touch the wrap to the roof and if i needed to reposition it it was no problem. Then I just pressed it down well when it was in position.
Now to the noise reduction part. As I applied the cement to the one of the central parts I found the roof would drum with just the strokes of the brush, and if you just tapped it with your pinky you could really get a loud druming sound. The sheet metal on the roof was so weak in that area I am sure that just driving down the road would be enough to make it drum constantly. I guess something must have dropped on the roof at some point that was soft like snow and stretched the sheet metal. I stopped applying the cement and I put a strip of Bequiet mat across the section, but that didn't solve the problem. I ended up cutting the mat and gluing (with heavy seam sealer) a metal stiffener across the section from rib to rib. This solved most of the druming. I had a short section of the metal left so I glued it next to the first one and the drumming was cured. I would have never noticed this if I had not been brushing cement on the inside. I never noticed it when I was sanding the top prior to painting. So in a round about way this has made the WMB much quieter.