They are almost impossible to flip even in the most severe weather and storms. Catamarans are very stable and have a natural high buoyancy, which makes them practically unsinkable with the sail down. Also remember, that because during strong roll, this feature of the catamaran becomes dangerous, since the center of gravity rises significantly above the center of buoyancy – in rare situations it is worth reducing the windage. But in general, if you do not plan to storm a tsunami or cross a hurricane, then you should not worry about the stability of modern catamarans.