As I just said in the poll, I don't think it should be an issue. The info available on 'historical loadout' is woolly at best.
I'm sure you'll all have read this artical, but I'll post the link anyway.
'The 'De Wilde' bullets were first issued in June 1940 and tested operationally in the air battles over Dunkirk. Their improved effectiveness, coupled with the fact that the flash on impact indicated that the shooting was on target, was much appreciated by the fighter pilots. It was at first in short supply, and the initial RAF fighter loading was three guns loaded with ball, two with AP, two with Mk IV incendiary tracer and one with Mk VI incendiary.
Another source for the Battle of Britain armament gives four guns with ball, two with AP and two with incendiaries (presumably Mk VI) with four of the last 25 rounds being tracer (presumably Mk IV incendiary/tracer) to tell the pilot he was running out of ammunition. It is not clear why ball was used at all; presumably there was a shortage of the more effective loadings. (By 1942 the standard loading for fixed .303s was half loaded with AP and half with incendiary.)'
'The 20mm cannon did not entirely rely on the M-Geschoss. There was still a requirement for some tracer rounds, so lighter 117 g projectiles were developed (by fitting the 134 g HE-T with a light-alloy instead of brass fuze), loaded down to around 585 m/s (1,920 fps) to match the recoil characteristics of the M-Geschoss. The effectiveness of the M-Geschoss was somewhat reduced by the fast-acting fuze, which detonated instantly rather than inside the target's structure, although this was probably more of a problem against bombers than fighters. The British rated the M-Geschoss as about equal with the 20mm Hispano round, which contained much less HE but had a heavier shell fired at a higher velocity and could penetrate more deeply. Delayed-action fuzes for the German shells were introduced in 1941. AP shells were also developed later and were not available during the Battle of Britain.'
I also think that trying to introduce server limitations would be opening the proverbial can of worms, resulting in lengthy debates/arguments which simply reduce everyone's enjoyment.
http://www.quarry.nildram.co.uk/BoB.htm