I just did something similar to mine last weekend. I simplified a little by using a 1/2 thick sheet of MDF and cut it out in the same shape as the styrofoam piece that sits on top of the spare. In that I cut the center hole for the exact same Pioneer 10" sub that you used. Once it sits into place (just like the styrofoam piece) I shimmed (sandwiched) some left over 1/2 inch MDF in between another piece of 1/4 inch MDF that I cut out to match the small corrigated piece of plastic that sits on top of the spare and under your carpet. What this did was make a solid deck that when I put the carpet back in, the speaker did not stick up above the floor level. I then put a level guard over the speaker to protect it and now I can put anything back there and don't have to worry about poking the speaker or anything.
The entire project took less than 2 hours and cost less than $20. System sounds great without a speaker showing anywhere.
I probably could, however because I've been unemployed for so long...all my belongings and tools are in storage which is about 400 miles away. I'm living temporarily in DFW looking for work down here. So I couldn't even consider it right now until I'm working again, and moved back into my own place. Sorry.
Your sub box is awesome. I planned to have some custom work done when I get back to Fort Hood. How much would you charge for a copy of your box? I was looking to do a 12" sub, but if I can keep the spare and be stealth like you, I will take a 10" sub. You are the man.
Your removal for the rearview mirror instructions are awesome. I'm actually trying to INSTALL the homelink autodimming rearview mirror since I purchased the base model Z. I was wondering though how/where does your homelink wire go to? I know it ends up down in the power junction box on the driver's side near the footrest. But where does it start? Is the line routed through the Center lights to the A pillar or straight to the A pillar? Thanks in advance.