Fiberglass mat or cloth?
 

Just wondering what is better for a fiberglass enclosure?

No idea...because I dont have a sub. But I felt bad that you weren't getting any responses.
Oh, and this really does belong in the audio section

check out this site for some useful info and pics of what you need and how to do it .

http://web.njit.edu/~cas1383/proj/main/

good luck and let us see how it goes...