Same. My middle seatbelt warning also goes off if I have two adults in the back seat. I have not done anything about it yet. I've only had my truck for two months. They just buckeled it up, but then it interfers slightly with the center fold down arm rest.
BlueBleed, if you proceed, can you let us know how it turned out? I assume the non-lux head rest pushed your head too far forward. Does the lux head adjust farther rearward?