[JLMounce]

For most of the popular cars out there, Dynamat also has their custom cut kits which provide what's needed in pre-cut sheets for easy install.

You only really need 50-75% coverage depending on the panel to achieve proper damping of the metal. Covering the entire car in the stuff gets you well into the point of diminishing returns, costs you more and adds unnecessary weight.

For large flat panels without bends or creases to add rigidity, try to cover about 75% of the panel. For panels that contain numerous bends and creases, you only need about 50% coverage on that panel. Remember, the constrain layer only dampens sympathetic vibrations, it doesn't knock down heat or air born noise like exhaust, tire roar etc.

A note on the different materials. Thickness itself is not indicative of performance. The "mat" products are mass loaded constrain layers. What matters most is the mass of the product, not how thin or thick it is. That said, it's easier to add mass with more thickness, but the material matters, it's certainly possible to add more mass with thinner material. That goes the same for the mass-loaded vinyl layer if you are using such a product. Thickness is irrelevant, it's the mass that matters.