fiberglass enclosure

well instead of building an enclosure or box.  I plan on just building one side of the box then sealing it  in to the back of my trunk. (98 Civic).  Thus using the back end of my trunk as the enclosure 5cu/ft.  I plan on using mdf and fiberglass.  My main concern is how thick I should coat the fiber glass resin to make the enclosure withstand the pressure from the speakers.  And what type of sealant or adhesive I should use to seal the fiberglass in.  I plan on using metal braces of course but I also need some sort of adhesive that can withstand the air pressure.  I have seen this type done in the past but I do not know exactly how to go about it. 

As for the ports I will put the ports leading up inside the cab of the vehicle so that it reduces some of the air pressure in the trunk while giving it a more bass feel

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