I haven't really followed this thread, stumbled across it not too long ago. My knowledge of aircraft comes from wikipedia. From what I remember just from memory, the P-39 was some average early war aircraft with poor high-altitude performance like many of its time.It was special for the engine in the middle and the 37mm cannon. The later sounds nice for killing bombers, but there the height performance sounds like an issue or as an attack craft. The former makes me wonder at first if the necessarily longer crankshafts were an issue, though I imagine moving the weight around could have different significant consequences, too, though no idea of for good or bad.