2002 td4 commercial seat belt conversion

Ive decided to put seats in the back of my td4 commercial the seats bolted in ok i cant see how the seat belts fit in though has anyone
ever converted one of these?.

all the mounts should be there in exactly the same place as the 3 door, maybe with a tie down ring fitted instead of a seat belt. Apparently (so I have been led to believe) the floor space at the back of the commercial is slightly wider than the normal 3 door, with a different interior trim panel to suit so the commercial has a better load capacity. Might be throwing your calcs out, or maybe worth removing the trim to have a look