A hybrid expandable restraint volume enclosure system incorporating at least one deployable semi-rigid human body reaction surface is provided. One or more walls of the expanding volume are substantially pliable, attaching at one end to a mounting base that is attachable to a structural member of a vehicle and another end attached to a semi-rigid deployable reaction surface. The energy absorbing expansion member may be thin walled or membrane-like and comprised of pliable rubber, plastic or a woven fabric. Methods of attaching a flexible expansion member to either a semi-rigid contact surface or a semi-rigid expansion wall of the enclosure include providing a mechanical attachment by capturing an expansion member edge between a frame and semi-rigid member. Material from a molded semi-rigid member may flow over or into geometries provided in a flexible expansion member for joining. An interface may be defined by blend-molding to transition different material stiffness.