I am just using plexiglass for the top, wich is about 650*350 (mm) roughly.... I did some research and found a plastic reseller here in my town. So I mailed them about doing the entire piece for me. Then I dont have to worry about cutting it properly. Allthough I havent goten any answer from them yet.

I want to build my own box, since I already have made my own design that fits pretty good in my car.

The ports on the box will be facing the backseat (placed in the trunk) And the speakers are facing upwards. Is that so good with the ports almost jammed into a 'wall'? Maybe the air circulation will get a little tougher? Because I want the angled side to face outwards, towards the trunk opening. Any thought about that?