Well, gladly, we have the 4.09 version of this lovely aircraft. The bird definately shows a lot of promise. However, there are still lots of things to improve there:
1) the external model: the upper nose section (supercharger intake or whatever it is) still not pronounced well enough unlike nose lower section intake
2) I have a gutt feeling that its flight model was borrowed from a European aircraft: it is way to heavy and sluggish even by WW2 American standards. I even had a hard time outmaneuvering Hellcats. Its climb rate is modest too. By 1944 standards, especially when compared to N1K2-J, J2M3/5 and even 1941 Bf-109F-4 it is still a "sitting duck." In reality this bird of prey was so potent that it should have had given the Anglo-Americans a tough time, of course, if its fate wouldn't have been so unfortunate.
3) Armament. The gun armament can be changed from default 2x20mm+2x13.2mm to 4x20mm. However, either option does not bring to any external changes: Type 99 Mk4 20 mm cannon looks quite different from the 13.2 mm Type 2 machinegun. The differences can be clearly observed on the A6M5c Zero where these two guns are installed in the wings side by side.