Having sailed catamarans on ocean passages for more than 60,000 miles in winds from flat calm to 60plus knots in the far southern ocean (around Cape Horn and Falkland islands), I believe 'Operator Error' is the primary cause of multihull capsize
Slow the boat down, heave-to or use a parachute sea anchor
from the bows according to conditions, including large breaking waves (parachute sea anchor) or strong winds (heave-to). Letting the boat surf at high speeds in large breaking waves tests the buoyancy of the lee hull
, that it might dig into the back of the wave forward of the boat and cause the catamaran
to pitchpole over that hull.
In the right conditions our catamarans could surf at over twenty knots and settle back to about eight knots in the troughs and accelerate again, under complete control, steered by the autopilot
, with no drama. At other times I would limit the speed by reefing to no more than 8knots, perhaps slowing to 4knots in the troughs.
It all depends.
The CSK cats have a good reputation and though an old model, I think are good boats.