Blue: Even with the quantity I purchased you've gotta budget how much you use and where. The areas that are hardest to service got pretty much 100% coverage.
I had to stretch the material to get all the places I wanted to cover.. thus the strips in the trunk, etc. I did not want to cover any threaded holes or fasteners in the door and this is why I didn't just put a sheet over the inner door frame. Besides which, unless you have a source of noise you don't need a 100% barrier.
I'm not a NVH engineer, so my approach may be totally off. I'll share with you the things I'm thinking about when I install the deadener:
-Heat requires a barrier to insulate the heat. Ordinarily I think 100% coverage is best.
-Sources of noise also require 100% coverage to obtain the best noise attenuation. Loud mufflers are a source, and 100% coverage will permit the best results.
-Vibration can be dampened by less than 100% coverage with strategic placement of the dampening material. Think about a drum, the drum creates noise by vibrating and moving air. A car isn't much different than a drum in the fact that vibrations will cause resonance of a body panel. While 100% coverage will eliminate any doubt of vibrations, examining which panels are prone to vibrating will reveal where you can place a piece of deadener to get the best results. You can silence a drum merely by placing one finger on the surface of the drum, you don't need to put your whole hand on the drum.. same principle. On a lot of large panels which tended to "oilcan" I merely placed a piece right in the middle, just like a finger on the drum.
You'll notice the area between the trunk and below the rear seat back didn't get much deadener.. this is because the metal is very rigid and not prone to vibrations. Conversely, the package tray area got pasted really well because it IS prone to vibrations. I use a really complicated and scientific method of determining where and how much deadener to use.. I thump it with my finger
I have yet to run the car, but I've noticed a big difference just working inside the car. I assume when I get the stock deadener and the carpet installed things will be much better than before.
While I used 72 square feet, I think 100 square feet would give you enough to paste the entire roof, doors, floor, firewall, and trunk.
Good luck on your project, Matt