"No valiant defence by the few, because the bombers would have been ripped to shreds. "
Brit jets with wot? 8 303.s?
A jet attacking a slower defended target needs a gun that only needs one or a few hits to inflict critical damage. Preferably at least 50mm as Germans calculated during WW2. But then again you need to make some calculations to hit the sweet-spot for optimal target effect considering: average closure rates, weapon effectiveness, hit probability, and weapon/ammo weights...
I know I know, there was Hispano 404 already...
That IAR-81 with BMW 801 would have been an interesting machine indeed.
-C+