im not sure how it is in the vert, but with my car, if you fold down that center piece in the rear seat (the arm rest) theres a velcroed piece of leather, pull it down and it reveals, the "ski" hole (i believe its called)?
anywho from looking at mine it appears to be precut so that it can be removed easily. So if you have the same set up pop out that piece and have your sub mounted right on or around that hole to get the best thump in the trunk.
By the way how much you spending on your one 10" sub?
Speaking from previous experience i put together one hard hitting system including 2 10's a 500 watt amp, speaker box and wiring for under 300 total.
The speakers were cerwin vega stealth series subs (one of the best subs out there in my opinion) 500 watt jensen amp (did its job) and it hit harder then my friends system which he spent well over 500 on a 12 inch 1200 watt sub and a 1000 watt amp.
something to think about if your building on a budget.
As I was walking up the stairs, I met a man who wasn't there. He wasn't there again today, I wish I wish he'd go away.