One thing I've noticed on Nacra boards is that the old ones that came originally with my boat had strips of carbon
fiber about 2" wide laminated on each side. I never broke one in normal use, but had one sheared off by a collision. The new board don't have this and was more bendy. Broke with hardly a whimper. Sounded sort of like someone rapped the hull with a fist. Mine broke landing off a wave. That's
when I noticed the lack of carbon.

Seems to me that if boards are going to fail, they would do it in the scenario you discribed. Sudden deflection at
high speed. You were about twice your normal going to weather speed so the forces were approximatly squared.