I havn't seen anything before suggesting different standardized armament in the 38 from the package we have in the game, but I'm not surprised at all that mods were made in the field, or that other gun packages were tested. Thats a good pic Guppy, thanks.
While more than 4 .50s could obviously be packed into the nose, adding a second cannon would be a different story, due to space and balance considerations. The Ammo and loading mechanisms have to fit in there, and if you load up the nose too much, you end up with an unbalanced plane that is more dangerous to the pilot. Flight manuals from the time warn against flying without ballast if the guns are removed, for example. What would the performance of the superstrafer version have been? Probably not as good, but I'd wager it would still haul bellybutton pretty well.
One possible shortcoming of the games depiction of these weapons is rate of fire. I've found advice articles written during the war that warn pilots against long bursts with their .50s. These claim that due to some kind of hop up kit that dramatically increased the rate of fire the barrels would soon be burned out with extended firing or overly repeated bursts. This could be why the 38 seems to suffer slightly in our game vs historical accounts. Still, the 4 .50s will reach out there really far for pecking and harrassing, have a good shotgun patter up close, and personnaly I wouldn't trade the 20mm for another two of them. Save the 20mm for up close and use all that ammo in the .50s for hearding and splattering.
Someone please let me know if you find info on how many RPG would have been carried with the 6 .50 version. I personally will trade two for more fire time, but I'm interested to know how the space tradeoff affected loadout.