Rear Pillar trim panels are easilly removed. I've had mine in and out several times. Its a van I added seats and belts too, then removed again. 1x Philips screw on each side through the lower trim piece then the upper piece just pulls out of its clips.
I had the spare wheel well with water in mine in the first year. Reported it to Ford and they brought it in for testing with hose etc. Im sure they replaced the seal around the boot and its not been an issue since.