question on enclosure for btl 18's

I drive an 06 infiniti g35 coupe and I want to attempt my first wall with 2 fi btl 18's. The deminsions to work with are approx. 44 L, 25 H, 26 D. I dont have any experience with buliding walls so I wanted some opinions on if that would be enough space for the subs and I have to build it inside the car so is glue and fiberglass resin strong enough to hold it together?. I usually see walls that are 14 cu feet after sub and port displacement, mine will maybe come out 12.