Wow. Thanks for all the information already Lanson. I hope I can be the person to start digging into the car and show folks what is there. Unfortunately time is tight around here. I could see myself ripping all the trim out of the trunk and starting there. Would that provide much improvement? I'm sure it would provide some insight into wiring. I already pulled back the left side trim and found, like the Taurus, that is where the amp is mounted. Also, thinking of a stealth install, noted that there are similar spaces on the right and other areas in the trunk where one could mount an aftermarket amp for a sub.
Ironically, the other car in my garage is a 2011 Flex. So it's interesting following your build. I will likely never do anything with that car though. It's my wife's daily driver now, and we plan to keep it after it's paid off to transport the troupes around.