Most Southern Ocean multihull passages have been in a downwind direction with the swell. While the Southern Ocean is certainly treacherous, the part of recent multihull circumnavigations where most structural damage has occured is while beating to weather in the Atlantic on the way back home. It's more about the wind and wave direction than strength and size.

These guys in the Hobart are beating to weather in horrible conditions. Minolta's cabin roof buckled inward because her keel kept trying to go downward and hull nearly collapsed from the buoyancy after landing off a wave. One of Skandia's huge canting keel hydraulic rams snapped in two leaving the keel swinging wildly. I don't think many multihulls would survive this beating. Upwind is hard on anything.