dampening material

Hello. I am in the process of building some sealed subwoofer boxes and I'm glad I found this site. It is very informative! Before I found this site I was browsing this one   http://diyaudiocorner.tripod.com/faq.htm and wanted to ask about this, and I quote

"Any enclosure can also benefit from the addition of 1" fiberglass acoustic insulation sheets stapled or glued to all interior walls (except driver/port mounting board). Some people don't like using fiberglass in ported designs, since there's a chance the fiberglass fibers may find their way out of the port and into your lungs"

My question is instead of using fiberglass insulation to line the interior walls will thin rubber matting work well? I have plenty of it! I also do not understand why I wouldn't line the driver mounting board side as well as long as I cut out the same hole that the magnet comes through? Thanks for any input!

Marc T

Depending on the density of the mat it might change the internal volume of the box if it is too dense, I would probably not use the rubber matting, try getting some Dacron or pillow stuffing and use this as it is not as dense.