Thanks fellas. Its nice to see highly respected sticks answer. Im going to settle on 400 for the Yank set and see how it goes.
If ya don't mind my saying, you're *really* limiting yourself by sticking to one range for all American iron.
Keep in mind what you wanna do that mission- if you're de-acking in a Jug, you'll want that convergence out as far as possible. But if you're going furballing in a Hellkitty, you'll want 'em somewhere between 200 and 300- that's where you're shots are gonna be (if you're patient enough).
If you're in a Mustang, however, you're going to be doing a lot of high speed passes, so you'll want your .50's extended quite a bit- more distance means easier to pull out before trimming the bad guy's rudder with your prop

I set mine at 400 on the 'stang. Same with Normal fighter op sorties in the Jug.
For the *REAL* close in work of the wildcats, I set mine to just about 200 even. THAT'S a lot of fun. You don't even need to lead all that much when you're that close.
Of course, P-38's are exempt, so just follow the Hartmann mantra of getting in close and tear 'em up.
With the .50 cal planes, convergence is just as important as your fuel load, IMHO. It affects their performance more then any other set. Make sure you do it right.
Just remember where it's set when you take off

More then once I've lined up on a bad guy at d400 for a tracking shot, only to lose him because I forgot to reset the conv of my Jug's .50's from the de-ack run 1/2 an hour earlier.