Fire power and all round defence would be the answer. A standard 23 only has 3 embrasures facing forwards and sideways. A Lincs 3 bay has six, two front, two back and one each side offering good all round defence on the very open coastal flats where they are most commonly found, and still has the AA position as a bonus. A good expedient measure to get a better suited structure using an adaptation of an existing FW plan.
