2x50cal are 50% more effective than 4x303cal in Aces High.
That's just a fact of the gun modeling.
Also, look at the relative SIZE of the ammo involved here. 50cal is a frakkin' large round. The .303 round is pretty small. You can store more than twice as many .303cal in the same space as you could 50cal (hypothetically, I'm not sure of the exact ratio, but there's a big difference).
Just because the 4x303s could carry 2400 rounds (FYI: a measely 600 rounds per gun, not much to write home about since they all fire at the same time) doesn't mean you can fit the same amount of 50cal in there. You could probably only fit 800 in the same storage space. Seeing that we have over 600 rounds (quoting you, not sure if that's total or RPG) is pretty close.
Anyways, the 50s are far better than the .303s ever were, especially at range. 50cals on bombers in AH going at 300+mph can hit a trailing target at 1.5k to 2k ranges. You put .303s in the same situation and you'd do NO damage until the target was 600 yards or less.* In the meantime the enemy has shot your arse off at 1k with his 20mm cannon while you were waiting for him to get under 600 yards.
50cals in the tail of the AH lanc is the only way it would ever survive an enemy engagement.
As for the stuka: It's not just a matter of popping gunpods onto the wings and calling it a tankbuster. It was a specialized variant with many changes to it that affected weight and performance. Karnak still believes it would need to be perked, and I still disagree. I think we'll see it someday. As for the 20mm version: I don't recall the details about what Tilt posted, but consider that 20mm used to be able to kill even the toughest tanks (the damage model has changed a lot since AH left beta). I'm guesing back then they wanted it to use bombs to finish the job and not just strafe everything in sight. Today, there might be a place for it, but all I can see is that it would be used as the IL2 is now, as a HO-tard base defense platform. It's so darned slow I've actually out-turned spits and ki84s in a ju87, got kills with the 7mms, and made it back. However I'd not want folks dogfighting with it if it had 20mms.
*In Hurr1 or Spit1 you need to be 300 or much much less (150 better) to do damage with these guns, and they have 8x of them. Taking this max range and doubling it because of the speed of the bombers and the target flying into the bullets, but that's still max effective, and not near the full punch of the gun.
