Sub box facing rear seat

I would like to maximize trunk, so I am going to build a single woofer truck-like box.  The seatbacks are basically foam with little backing, I am planning to make a long, tall, thin 1.0 volume sealed box and angle it against the back seat.  This will take up very little room, but I wanted to make certain that it would not minimize accurate bass.   I believe if I aim it towards the trunk, it might be louder, but my car has almost no sound deadening for weight, and there is a big wing on the trunk, so I am worried about vibrations.   

The wing is on the rear because you need it to keep your car on the pavement when you're approaching Mach speed...right?  So, it looks like you have that important step done.  Next, and equally as important, is to make sure you have a big fat tailpipe that gets real loud....

But to have good-sounding bass, you will need to overcome all this with sound damping.  Until that is done, no matter how you build the box, or how you aim it, the sound of bass will be weak and the rattles will ruin it.  You will most likely need to adjust the tension on the trunk hinges to compensate for the extra weight...normally necessary even without the addition of an aerofoil wing.

You can build an enclosure that is very shallow as long as it meets the space requirements of the sub.  Make it strong and well-braced.  Consider, also, inverting the sub to allow the box to be as shallow as possible.

I new what I was asking for when I gave details about the car, but it came with little deadening and huge wing from the factory.  The car was too fun for me to pass up, and would have ordered without the wing, but you could not.  It has grown on me by now anyway.  As far as making the box strong and well-braced, I was going to use 5/8 mdf, but coat inside and outside of box with fiberglass resin.  I can imagine what you mean about inverting sub, but can you provide more detail. 

Jvee, sorry for the attempt at early morning humor there.  Your car is no doubt a nice ride.  But to the point:  the box you build, being flat in nature, should have more rigid walls than 5/8".  The larger the area in square inches of any wall, the thicker it should be.  I would use the standard 3/4, although your experience with fiberglass resin coating may prove me wrong on this.

If I had an enclosure that looked something like this, I would add a brace from front to back in the center of the largest expanse of field, like what is shown with the red dot.  And more bracing on the other side of the speaker hole, also in red here.  That will help prevent flexing of the front and back panels.  The sub in this case would be inverted, as there is not enough depth to fit the entire speaker into the box.