1/2"??? From 7-8 layers?
That's gotta be some thick matting y'all are using.
Typically, 1/4" is fine, depending on the sub you are using. If you're planning a Brahma with 1000 watts flowing to it, 1/2-3/4" would be better.
Thicker is always better, just not always necessary.
I've got 7-8 layers on my enclosure, and it's about 1/4" thick. I can stand on it without breaking it or even flexing it.
~HH