I can confirm you will rub the spare sidewall and use the hitch and bed rock rails a fair bit when wheeling it. Definitely not the ideal place for Offroad.
Try it again. Slide it to the end [the rectangular cut out] and it'll pull out. To move it to another rail such as behind the cab, insert into the rectangular cut out and slide to the desired position. I was able to easily move cleats between the rails.
Haven't been able to find...