The optional seat belt kit which we ordered through our dealer consists of
the two seat belts, the back bolster (a long and a short piece), a back board
that mounts behind the bolsters and a seat cushion to fit between the two side
cushions. The holes needed for mounting the seatbelts were in the metal piece
under the back cushions when we bought the RT, making the seatbelt option possible.
Note: in most cases when just the two of us are travelling, we leave the rear
bolsters at home and the seat belts tucked away.