John, Sorry didnt answer all of that. The Hispano canon where actually fitted to a squadron of Mk1 (or 2's I cant remember) during the battle of Britain. I think the fear was that the Luftwaffe would armour plate their engine bulkheads making the .30 browning ineffective. It wasnt a great success, the guns would often (like all the time) jam. The early hispano;s used a big drum magazine but I think it was the ejection port that would jam. By the time of the Mk5 they had settled down and sorted the problems, mostly. At some point later the drum was lost and the rounds where belt fed, Around mk18 or so I think. Kev Skyhawks mob, 19 Squadron, flew the cannon armed spits in the BofB ad had a torrid time with them. If memory serves, they swopped them for eight gun fighters from an OCU? Douglas Bader commanded the Wing that included the cannon Spits during the BofB... he refused to fly one in 1941, even after the bugs had been ironed out!