"So, four years later, has this been resolved to anyone's satisfaction?"
As it turns out, I have a very good friend who was part of the NTSB team which investigated the crash and reported last November. Their conclusion was that a spark in one of the fuel tanks was the cause.
I am still unconvinced. As more information about the circumstances came out, the coincidence of the navy training nearby causes me some concern.
That said, we must accept the conclusion of the NTSB since we have no way to get contrary data.
That's my opinion, I am unconvinced, but have nothing else to go on.