Placing the Bell P39 Aircobra.

[tcolvin]

This aircraft was rejected by the RAF without reference to the Army because of an irrelevant lack of performance at altitude.
It was fitted with a cannon with a low muzzle velocity suitable for knocking down bombers but unsuitable for killing tanks.
The engine was mid-mounted and therefore less vulnerable to ground fire.
The Russians fell in love with it. The British Army never knew it. The USAAF were ambivalent.
What were the pluses and minuses of a unique design?