custom sub box

[yaris2010RS]

hey all, i have a 12" shallow sub mounted in a sealed custom box. i am planning on remaking my box (i break it atleast once a month) my old ones have been made of wood but i want to make one out of fiberglass. how is fiberglass as a sub box medium? in my entire system the sub box has been the weakest link so far.

i know sealed box isnt the best so if anyone can give me some pointers to making a small ported box let me know. i dont know the subs ported specs off top of my head, but sealed box specs were 0.6cubic feet. as a guide the sub sits where my spare is ment to go.

also the box is anything but a "normal" shape

my biggest problem is i dont even know where to start with this project. any opionions are welcome.

thanks