Nice looking kit.
Wayne/Heinz, A4K is more or less right, but there's a bit more to it than that. The designation, i.e. B,C etc, stemmed from the wing type, and the cannon bulges were placed according to fitment of weapons. The 'stub' fairing for instance, could be a capped, redunsant tube for a cannon, or could mount a Browning .50 cal. This could be inboard OR outboard, depending on fit!
The main 'problem' area is with the MkIX/XVI, where the bulges can be confusing; the MkV series wasn't quite as bad, although the MkVc was not neccessarily tropicalised, again it was a 'C' wing, designed to mount 2 x 20mm per wing, although this was not a common fit.
Terry.