I just got my C-Max last week - Ordered it for flat towing behind my Gulfstream Tourmaster, and just got through installing Roadmaster base plates for my All-Terrain tow-bar. Everything fit OK, but the instructions had me cutting away the energy absorbing panel and removing the air duct to the A/C condenser. With a little trimming, I was able to retain the air duct and replace the majority of the panel when I re-installed the bumper cover. I think Roadmaster needs to re-think their instructions.
I also installed independent rear lights so I didn't have to interfere with the existing wiring.
I searched for more info regarding the keyless entry & towing, and found this forum. After reading this thread, I am not thrilled with the dead battery issue. Even if it is easy to jump start, the battery is not a deep cycle battery and totally discharging repeatedly it will shorten its' life.
This afternoon after I finished the installation, I tried this for my test tow of about 5 miles. After hooking up, I touched the start button to turn everything off and then got out and shut the door. I then re-entered the car and manually over-rode the shift lock to put it in neutral without touching the button or the brake pedal.
My owner's manual showed removing the right side of the console to reach the shift interlock latch, but it didn't provide access. I pulled up on the shifter boot / trim plate around the shifter and it popped loose. Looking down into the opening, on the left side towards the rear of the opening there is a white plastic lever. If you press the start button, touching the brake pedal will cause this lever to move. If you manually move this lever to the rear, the button on the shifter can be depressed and the transmission can be shifted into neutral.
I haven’t made a long trip, but it dash was dark, and it was not nagging me to put it in park. I tried this with the car on jack-stands, and the wheels were free to turn and steer.