[Graham Boak]

I think you've both made good points, but I would point out that neither had fuel tanks in the wings (except the later Mk.VIII Spitfires, which is irrelevant to the discussion, but has to be cleared out of the way!) Both the Hurricane and Spitfire wings were stressed skin, with most of the loads carried by the spars and ribs: I don't see that it would be any easier to add strengthening structure in one or the other. The truss structure of the Hurricane only extended out to the undercarriage. I suspect the Hurricane required less redesign to take the cannon, because of the large weapon bay for four guns rather than two, but this alone can have little effect on the quantity choice of ammunition.

One question I have - did the (as originally desired) 4-cannon version of the Spitfire c wing retain the 125 rounds per gun, or was it then restricted to some 60 per? In which case the two types have much the same, and the answer is that 60 rounds is what the appropriate experts thought necessary.

The point about weight is well made: for both fighters, the 4-cannon version was considered restricting on performance and handling, and saw one pair removed. This was normal on the Spitfire, if less so on the Hurricane.