Pongo, the big advantage of the B-17, B-24, and B-29, was their defensive armament and the fact they flew in massed formations.
The myth of "heavily armored bombers" is just that, a myth. Bombers like fighters have very little armor, and then only in a few critical areas. The thing that probably helped them the most was that self sealing fuel tanks were standard issue, and they had 4 engines, instead of 2. And then you could get home on 2 engines, even with 2 shot out.
Even with all that, the B-24 was known to be much more vulnerable than either of the other two.
And the B-26, while armed with .50's, isn't much better defended than the Axis bombers. It has what, 4 defensive guns?
Many of the Japanese Bombers had 20mm cannons in the tail guns, and the other positions had 12.7mm MG's. And one of the Japanese Sea Planes which doubled as a bomber, actually had 5 defensive 20mm cannons in flexible mounts.
Even so the earlier Japanese Army aircraft armed with x4 12.7mm MG's regularly engaged US bombers. The Russian fighters mostly armed with a single 20mm, and x2 12.7mm MG's regularly shot down German bombers. And I already discussed the American Fighters. Hell, the Brits used rifle caliber MG's to shoot down many bombers early in the war.
My point is that the "Tank Buffs" are a total myth. And that you do not have to have a minimum of x4 20mm cannons to even consider getting a kill of a bomber.
------------------
Vermillion
**MOL**, Men of Leisure
Carpe Jugulum
"Real Men fly Radials, Nancy Boys fly Spitfires"