... in a waterproof pouch. A PLB clipped to your life vest is another option for backup.

One other lesson from that story is that de Lutz left the cabin too early after they turned turtle, as it sounds like he was lucky to get back aboard as the boat righted again. It was a risky move and he could have been separated from the boat. Yes he was rightly worried about saving the raft, so this judgment is with the benefit of hindsight (as they didn't know they'd be righted again).

Apparently the raft was rigged to automatically inflate (which caused other problems). Perhaps manual inflation is a better option?

Another thought is that one can't swim down and out from under a capsized boat if your PFD is fixed foam or automatically inflated. For this reason I think manual inflation is safer.

As a coastal sailor my thinking was that my submersible handheld VHF (with integrated GPS) is a sufficient backup. My boat is unsinkable but my Achilles heel would be capsize, or fire is another potential concern.

My EPIRB would trigger automatically if we capsized, and that's the way it should be on a multihull that can't self-right.