In projects i've worked on, we came up with a maximum laydown angle of 17 degrees, meaning from the normal vertical, in 120 kph winds.  beyond that, we detuned the turbines to keep the angle upright (no greater than 17 degrees).  We have no real world data on whether that was the correct decision, but even if wrong, we don't lose much energy if we have to derate sooner.

"Life shrinks or expands in proportion to one's courage." - Anaïs Nin