I've got the same model camry, just without the sunroof. I currently have a 15" fi sp4 in 4.6 ft3 tuned to 31 hz with an 8" aero on a sundown 3k. Sub back, port firing into driverside of the trunk. Hits 28-35 really well, but rattles the trunk lid/underside of the rear bumper like crazy.
I am thinking about doing something very similar to what you have here. Just wondering if you ever had a rear firing set-up and how it sounded vs the 12x2 sealed off. Really don't want to spend 1k on subs to find out it kills the lows forward firing.
What size/tuning was this box and aero? And which btl? My N2 15" I just pulled out has some issues, lol.