I have only done that once. It was on a 5.5 uni. The wind and waves just kept building. I kept going deeper and deeper on the downwind legs, just to survive. On one leg, I was going nearly dead downwind, topped a monster swell, felt the wind go calm (you are now going dead down wind at windspeed) and watched the water rocket toward me. It took 3 people to keep the boat upright long enough to get on board and head for the beach.

I really do not know what to do to regain control. I had reached the capabilities of me and the boat. Now, when I am in danger of pitchpoling. going dead downwind, I go to the beach.