McSorley's calm 'we are holding our own' is a kind of proof that the end came in a sudden freak event like the ship breaking in a deep trough, as has been said above.

Overload seems like one of those things easy to calculate by the investigation team. If they didn't find it a cause, I don't have a big reason to doubt it.

Chris, I don't know about the audiotape, I think the various videos and stuff is available through the
Great Lakes Shipwreck Museum / Fitz subpage

I recall reading a play '10 November' which got into an issue regarding one of the unmanned lights along the shore being out of repair.   Was this ever discounted fully as a contributing cause? If radar was not working, then a missing light could have led to miscalculation bringing them too close to the shoal.