IIRC, U.S. forces in the Pacific used slightly different belting when flying against lightly armored Japanese planes, more incendiaries, less AP.
As JtD said, API/APIT belting isn't unreasonable for U.S. planes from 1942 on, nor is it unreasonable for allied British, French or Italian lend-lease planes.
The simple and necessary thing to do is to change the number of M2 options in the game - M2 Early War, M2 PTO/CBI Late War and M2 ETO/MTO Late War.
For that matter, TD will need to add some additional options for other common weapons, especially if they plans to release any nightfighters or night bombers (no tracer ammo).
It would be really cool if players could select their own ammo belting, but that would require way to much work.
