Abstract: An add-on structural support arrangement for a convertible-type vehicle rear passenger shoulder belt system comprising a pair of mirror image composite pillars fixedly disposed at each rear corner of the rear seat compartment. Each pillar includes three vertically elongated sheet metal members, i.e. a forward seat attaching panel member, an intermediate anchor panel member, and an aft channel member, substantially coextensive in length and welded in flatwise abutment. A horizontal tie bar interconnects the upper ends of the forward panel members, while lower oblique wing of each anchor panel member is bolted to an associated portion of the body floor pan. A shoulder belt retractor is mounted on a lower rear face of each pillar while each aft channel member provides a vertically extending guideway for passage for its associated shoulder belt. The anchor panel is formed with a U-section in cross-sectional view defining a pair of side flanges each provided with a midpoint attachment ear.