The flex of webbing accomplishes this job just fine if the harness is configured properly. Harness Materials Harness materials should meet mil-spec., but that is not enough. The material must be used as design intended. Refer to The Parachute Manual, pg. 80 - , sections 4.060 through 4.062.
Most manufacturers use open cell foam that they buy at the carpet store.
Buy a rig that uses closed cell athletic padding that will float and not absorb water. There are several variations of this design in use. Due to some recent incidents where cutaways have been from difficult to impossible, I would anticipate additional variations or improvements. The 3-ring is a single point riser release system designed around three rings of decreasing diameter. Each is able to nest inside the larger with clearance for mounting webbing.