be careful with your box volume...some subs are extremely picky about box size. boston pro 12" (what i have) require EXACTLY 1 cubic foot. more or less and you'll damage the sub. this is one of the reasons tweeter is phasing out sales of those subs...too many replacements because of bad box design. i love them tho...one of the best i've heard in the price range.

fiberglass is difficult to find volume from...if you have the room, try to build a solid, regular shaped (squared off) 3/4" MDF box and use fiberglass to surround the box location for whatever design you are trying to do. fiberglass can be a bitch to leakproof, especially in high SPL installs.