I made one for my 2G a couple years back. It looks like you used the stringy Fiber glass stuff......I'd recommend adding some very thick layers of fiber glass matting. It's super thick and can absorb a lot of resin, which is what you want for overall rigidity.
In the back, I believe I did 4 THICK coats of glass with a frack ton of resin. Hopefully you took your time and made sure that there were absolutely no air pockets between layers and gave it ample time to dry.
To eliminate air pockets while using the fiber glass matting, I cut the matting into various size squares/rectangles and put them down one at a time using smaller batches of risen (it'll harden too fast and you don't want to rush this)
After that layer dries fully (I gave it 24 hours for each one), get out a little air sander and make everything smooth. Rid of all the little whispy ends from cutting the matting. Once it's all smooth, scuff it up a bit and start all over.

To get the fleece on the front, it looks like you did something similar. I stretched it over and glued it on using 3M spray adhesive. Worked like a charm. At this point, it was all resin. again, another THICK 4 coats on the front, allowing for proper drying time and coating it over the back, blending into the base/backplate.

It cost me about $200 in materials to make and weighs about 15lbs before the sub is installed. ROCK SOLID though! I'd recommend some weather stripping along all edges and corners to ensure it doesn't rattle or vibrate against the plastic trim.

It's looking good though. When she's all stiff, it'll sound amazing too. I get a super deep solid hit, and mine is a dual VC 10" infinity.

http://www.ca.dsm.org/forums/ubbthreads.php?ubb=showflat&Number=405885#Post405885