Zaplead, I find your question interesting, but trying to see the relevance to Bill Deacon's tragic incident. He was down on the deck of a cargo vessel, I don't think a CVFDR would be any different to a CVR in helping determining what happened below the aircraft.
Are CVFDR's of the same size as FDR/CVR's, if so, do aircraft carry 1 CVFDR or 2 for redundancy?