Uhmm, B17's went down pretty easy when hit by 20 and 30mm. Just watch any gun camera fotage and you'll see that in 95% of those films the gunners are not shooting anymore, no armored glass, specially not as thin as the turret gunners/tail gunner had can protect from cannon shells not to mention a waist gunner.
The problem with buffs is that they outperform fighters above 25k or so, even the TA152, which was, and still is (if there were any flying) on the very edge of what a piston engine plane can do, that means at what alt and speed it can reach, specially alt.
No other piston engine plane has every been able to compete with its high alt performance and yet B17's outclimb it at 30k?
One way to acually limit high alt use of bombers and fighter would be to modell high alt preasure. When you reach an altitude of about 30k or so, a bit less even, and don't have a preassurized cockpit you're vision narrows down and your boddy starts to hurt aswell as you get weaker. I have the pilot report from a TA152 pilot who brought a TA152 up to about 40k or so, the cockpit preasurisation was broken.
Now, the only fighter in AH, and (I think) the only fighter to see service in WW2 with a preasurised cockpit was the TA152, modell that fatigue and high alt preasure in AH and the TA152 would become the high alt beast it was capable of (we all know they used them mostly as low alt field defenders).
Modell the narrow vision and thus buff gunners will have a hard time shooting, modell the weak muscells by making gun movement slow, sluggish and make them wobble. Allso add gunners passing out at extreem alts, much like pilot wounded.
