The purpose of redundant buoyancy is to provide safety in situations in which dichable lead is not an option.Interesting. The one option for redundant buoyancy that you skipped was ditchable lead. The likelihood of a runway buoyant ascent with a DSMB or lift bag (especially if you are clipped onto it seems very high). My wetsuit rig is set up so I could, if absolutely necessary, ditch increments of lead (two weight pouches and a weight belt).