Why the Italian MAS formula reached its limits

The Italian MAS remained a very fast expression of the World War I torpedo-boat formula, but that specialization left little room for wartime growth. Its light structure and narrow weight margin limited additional guns and equipment, while even Mediterranean rough weather could take away the speed on which survival depended. Paper speed could also be misleading: a broader-beamed Fairmile D started slower but could retain enough speed in severe North Sea weather to become effectively faster than a Schnellboot. Rapid-firing four-inch weapons on larger ships could tear through the lightly skinned boats once conditions slowed them enough to be hit. Adding night-fighting or convoy-escort equipment was possible, but each increment made the MAS worse at its primary high-speed torpedo role.