One thing to keep in mind with SEVERAL planes in game, is that the default head position is lined up with the gunsight, NOT the center of the plane. Look at the canopy frames themselves. Shift your head left until it's centered, and I think you can see both cannon barrels (maybe, it's been a while since I tried!).
As mentioned, that other protrusion is the gun camera, but I don't think I've seen that real 190 pictures, so I dunno why it's in AH.