SHOBoat, sent you a PM regarding your box dimensions. I know this thread is old, but I'm replying anyways.
I just purchased the materials to do this myself, but I'll be utilizing a single 12" and a 3000-watt monoblock amp, with the AudioControl LC2-i.
I'll take some pictures and start a new build thread of mine. I hope it turns out half as good as yours did!!
As for the questions regarding a spare tire ...... I pay for AAA for a reason. I typically run staggered wheel/tire setups and spare tires are useless because the sizes are extremely off, or I'd have to carry two to make it worth while.