I was able to complete the GTMat installation yesterday. First, I apologize for the grainy pics and bad lighting. It was raining both days while I did this so I just left the car in the garage.
Removing the interior panels:
Everything removed (the next day lol):
GTMAT installed!
I did have a few leftover strips that I slapped over the wheel wells after the last pic. Using the 10 sq. ft. I was able to cover maybe 1/2 the hatch area. It looks like more, but there is a lot of vertical surface left uncovered. The product is pretty easy to work with and total installation time probably ran 2.5 hours. I'm sure I could go quicker now after working with the product and understanding how to remove all the interior panels. I was able to mold it into place without much trouble leaving very few points where contact isn't 100%. I can't say I'm looking forward to completing the job since the remaining areas are going to be more difficult, but after hearing the results of partial coverage, it is something I plan on doing.
My exhaust is pretty loud, and the tire/wheel combination definitely adds to the road noise. I only have the base stock sound system (something else on the to-do list) so I can't comment on any improvement there. Upon starting the car, I immediately noticed the exhaust was slightly quieter inside the cabin. The road noise reduction was also apparent, but not as noticeable. I didn't measure decibels, but there was some noticeable improvement from partial coverage on a very loud car. I do believe the additional reduction in noise with 100% luggage and door coverage will be worth it and would be even more so for a stock Z.
I may wait a couple of months for the weather to cool off and hopefully do some speaker replacement at the same time, but I will be completing the job using GTMat.