It turns out that I didn't need any extra weapons.
Tried out the birds, to verify that they work. I had a couple of CTDs, before figuring it must result from my modded classfiles which incorporate the gear damage mod (and probably other stuff), as well as improved compass behaviour. So I simply replaced the classfiles included here with my own. Seems stable now.
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I note that the F and K use the M cockpit. I should think they should instead use the E cockpit. I've already altered the F class file accordingly, and am planning to do the same for the K.
That's because the principal difference between these 'pits in our game is the gun sight. The E was fitted with an early N-2 sight, which had the sight head as a cast piece having triangular metal sides supporting the reflector plate. Some of you may already be using my sight mod for the E, and know what I'm talking about. (My F4F-3 has a similar sight head, albeit of taller form suitable for the generous look-down angle over the cowling on such Navy fighters.)
I've seen pics of the K having badically the same sight head, albeit with the sight body lying horizontal and having an intermediate mirror housing. But fundamentally the same basic sight.
As far as I can tell, it was only later '40s which were fitted with the 'cleaner' sight head having just the reflector plate glass protruding up from the sight head. As for my sight mod for the M, which I hope you all are using.