as far as using the box on it's side, i don't think that you can use it otherwise in a car. i'm using mine in-home and it sounds better laid on it's side, because the woofer was sag.
try diffrent firing positions. since it's got a square "footprint" you can try anything. i'm not sure, since i haven't tried mine in a car ::). what sounds best is best.
i cut every round cut on my DBs with a jig-saw. i guess it can become very difficult to cut speaker holes using a circular blade
:-/.