building custom fiberglass enclosure, not a how to? more like tips Options

[Element23]

Im pretty much finisehed with the planning and drawing stages of this project but i just wanted to see if you guys had any tips. Im gonna be using styrofoam to mold it, using a heated styrafoam cutter. also im gonna be using MDF board at the base of the whole thing with mdf pillars and an MDF board that will line up with the back of the rear seats. However, i was wondering if this is a good way of doing it? I want to keep my existing carpeting and creating this type of mold with an MDF base and sides will give it good styling and a clean look. any tips?

[Element23]

also, i forgot to mention that the whole thing will be rounded and designed based on an angle of about 30-45 degrees horizontal to the bottom of the trunk, angleing upwards towards the seats. Also while the subs will be angled at the angle, they are also gonna be angled towards the sides of the trunk at an exact 36 degree angle. in my head, this is a good design, but we'll see when its being molded. also, where do you guys feel i should position my amp?