I've never been close to turtling mine, although I've been in some exciting conditions.
Crossing the Strait of Georgia
on a beam reach in 4-5 foot seas and 20-30 knots was one.
We averaged 13 knots for the trip, hand steering
the whole way because the autopilot
couldn't keep up.
I wouldn't have trusted it anyway in those conditions.
A couple years ago on a delivery
of a DF35 to Southern CA, we were rounding Cape Mendocino, had an incident and came really close to a capsize
I posted about it.