Image copyright by Kow Yokoyama. The PK41-5 was modified from captured PK40/41 machines. The nose was redesigned and given additional armour, while the indirect sighting system was added to the craft. 12 machines were modified (although only 8 with the indirect sighting system) and to these machines were added experimental anti-gravity engines. The original landing gear of the PK40 was removed, as it no longer had the strength to support the new PK41-5. Instead, a special type of low-pressure balloon was added for landing. These balloons had been lying surplus in a warehouse, and when the second lieutenant grasped the concept that these balloons were going to be used as landing gear, managed to order so many of them that the warehouse became known as the "Balloon House" afterwards. With the capture of the Shutoral Firefly, the original 14.5 mm machine gun of the PK40 was upgraded to a 23 mm cannon. Ultimately though, the PK41-5 would prove unsatisfactory in testing and no more would be developed.