I admit I don't know much about the US specific units, because it's hard to keep the numbers lined up with what they did. I mean, take the P47 skins I made. EVERY time I wanted to know what FS/FG they were in, I had to look up what I'd written down. I just can't remember pure numbers. LW numbers are a little easier to understand because you'll have less numbers with more gruppes per number. RAF are a little easier to remember because they don't have FS/FG, just "xxx Squadron". US number have always eluded my ability to remember them, so I can never say for sure what goes with what.