Prior to designing a new thorax/abdomen system for the Hybrid 111 frontal crash dummy, an exploratory effort of alternative design approaches, other than damped-steel ribs, was undertaken. The primary emphasis was on use of internal response elements consisting of fluid-filled, inextensible compartments with orificing to a gas-filled accumulator. The impact response characteristics of the chest to blunt, rigid impactors would be achieved by the combination of fluid mass, fluid flow, and compression of the gas. Although this approach was not used in the Prototype-5OM design described in Volume 1 of this report, some successes were realized. This report describes the research activities and results from exploration of a variety of fluid/gas-based design configurations, as well as activities and results from exploration of compatible solutions to chest deflection instrumentation.