The 55SX can also be configured with three cabins below deck -- in this layout, the third stateroom sits to port in place of the galley. Configured here as an on-board office, the cabin features a convertible settee along the port side, which can easily pull out to create a berth for sleeping. A fold-up desk is included at the forward bulkhead, and the single cabin door is replaced by sliding pocket doors. The rest of the lower accommodations are consistent with the standard deckplan.

To make room for the third cabin, the galley moves up to the aft end of the salon, with pass-through access to the cockpit through a retractable salon window. To starboard is refrigeration and galley storage, just aft of the entertainment center with pop-up TV. To accommodate the up-galley layout, the main settee here moves forward, opposite the helm.