Roof insulation

[makoshark]

Covering only 25% of the panel is sufficient in reducing the amount of harmonic vibrations. Dynamat Xtreme and the equivalents are not sound deadeners, per-say. The do reduce the amount of road noise by reducing harmonic vibrations that are translated through sheetmetal. A true sound deadener is a Closed Cell Foam and/or Mass Loaded Vinyl. These need to be used in conjunction with a dampening mat. However, I prefer to save on weight and not use Mass Loaded Vinyl. A thin layer of closed cell foam, strategically placed Dynamat Xtreme along with the regular jute padding under the carpet will greatly reduce exterior noises and save weight.

[fordsbyjay]

So I'm going to guess the best places will be large flat areas. Areas with bends and shapes would be less likely to vibrate then.

[makoshark]

You are absolutely correct. Focus on those flat areas. If you have mat left over, then you can cut small pieces and hit the other areas that include inner structure of the car.