Remember to be realistic in what you expect from these products. They all kind of work in some way or another, find the right product for you can be difficult and expensive. Like Scott said paint stuff on can be a bad idea, if you are just doing it to see if it works. For example most of these products will not stick to the rough surface of a bed liner and paints won't stick either because the bed liner once dry is immune to solvents (well almost).
The mog roof on the double cabs is kind of flexible and the interior noise reverberates. I used two layers of heavy butyl stick on stuff, the bottom layer does not have the foil so the top layer with foil stick perfectly to make a single thick layer. I also used the home depot foil bubble wrap insulation for heat and together they worked really well. I also put paint on bed liner on the outside of the roof to hide some fading paint but it made absolutely no difference to the interior noise or heat. I don't know if it would of made a difference if I hadn't already done the interior work. I would guess you would have similar noise problems inside a van.
In the front of the cab all these off the shelf sound proofing products are simply not heavy enough to absorb the noise of a 6 liter diesel when you are sitting only 18 inches away from it. The best solution for the front of the cab was very heavy rubber. The mats on the floor are about an inch thick and must weigh about 30 pounds each, these made a huge difference. I also got a n insulated heavy rubber dog house cover, specially made for a mog. This weighs about 50 pounds and together with the mats and the roof they make a huge difference.
Rob
You don't inherit the world from your parents, you borrow it from your children.
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1979 Unimog 416 Expedition Camper
1974 Unimog 421
2004 Dodge Ram 2500, 4x4, Double Cab, Cummins Turbo Diesel
2006 25' Airstream International CCD
2009 Harley Davidson
Sugarloaf, Boulder, CO