In 1944–45, during the last days of the war, it was modified as a high-altitude interceptor, with two 20 mm cannons in the nose and one 37 mm (1.46 in) cannon in an "upwards-and-forwards" position – almost like the "Luftwaffe"s "Schräge Musik" night fighter cannon emplacements – for fighting USAAF B-29 Superfortresses over the metropolitan Japanese islands. It lacked stability for sustained shooting of the 37 mm (1.46 in) weapon, had only a thin layer of armour plating, lacked self-sealing fuel tanks, and was slow to climb.