Customize Stock Sub Location with FG

I am considering replacing the stock sub in my 2003 Honda Pilot.  To date I have found very little on the subject other than driver swaps and mount depth extensions.  Rather than just put a new driver in, I would like to seal the stock location...it doesn't look as though Honda sealed it too well.  My first thoughts are to use fiberglass but I would entertain other suggestions.  If fiberglass is the best option, what would be the best way to create the enclosure?  I have attached pictures (not my vehicle) of the stock location with trim panels removed.

Please give me suggestions on the best way to seal this mounting location so that I can get the best possible performance out of a driver change.

Thanks.

-Chris

Thanks for the reply Aaron.  To give more information, the existing hole is cut for a 10 inch drive with 3 inch depth.  Since it is not deep enough to accommodate most aftermarket woofers, a bezel must be made.  No big problem, I've done that before.

As for the panel, it is permanent.  It only comes off once, if you know what I mean and I am not about to start cutting huge chunks out of the panel.  So, in short, the only access to the inside of that cavity is through that 10 inch hole.  So with that, the question remains, can a fiberglass enclosure be created through a 10 inch hole?  Or the real question is, should a fiberglass enclosure be created through a 10 inch hole? 

http://www.hondapilot.org/forums/showthread.php?s=1233d56afc0dec82f1ca882c6f69d7ff&threadid=10630&highlight=fiberglass (look on the 2nd and 3rd pages for more pictures) This guy had an enclosure fiberglassed in the factory subwoofer location. It wouldn't be very easy to do the same thing though.

I would reccomend just using a MDF spacer and mounting a decent 10" sub that is capable of running free air in the factory location. You can seal up some of the small holes in the sidepanel with something like dynmat. You should probably use some sound deadening material (like dynmat or fatmat) on the metal sidepanel the woofer is mounted to and the metal panel behind the sub.

Thank you all for your help.  I think that customsuburb has the right idea though.  I spent countless hours on the hondapilot.org site looking for exactly the thread customsuburb linked.  For whatever reason, I couldn't find it.  I guess it is time to plug in the sawsall with the metal cutting blade. 

On the other hand, it may be possible to replicate what that guy did through the stock opening.  It looks like he used two boards to seal the top and side then a few layers of glass and resin to seal the whole thing up.  It also looks like he used a 12 inch driver which I don't think I need.

If anyone has any advice relating to the task of glassing the enclosure through the stock opening, I am all ears.

Thanks to nstlfrk for the Pioneer link (didn't know they made shallow subs that could handle power) and continued thanks to Aaron for his suggestions. 

-Chris