and since we're on the subject of convergence...
How much in our game does it make a difference I wonder.
If I snapshot an enemy with .50s at a range of 200, what would be the difference in damage if I was converged at 400 vs 200?
I understand how this would work in RL but how much of a difference in AH 
Once you learn to land hits with the crossing shots at around the D200 range (an actual 300yards) you'll be much more effective with a brief shot if you have all of your guns focused to a single point at that range (by having convergence set at about 300yds. A brief shot with .50's set like that (and at that range) will zip the wing right off of almost any fighter in AH like a chainsaw.
Hitting a fighter at
any range other than what you have your convergence set will do several things. One of those is that it'll split your bullets into two separate groups rather than one (this almost always happens anyway, because you're almost never able to maintain exactly the correct distance from your target). This is bad though because it ensures that
none of your bullets will go where you're aiming, and that they'll be split into two groups (one or both of which may miss your target completely).
As range increases bullet spread increases due to the modeled dispersion as well, which means that if you have your guns set for 400yds and hit a target at 400 yards, your bullets are spread out more than they would be if you had them set at 200 and hit a target at 200. The bullets are slowing down as well. Overall, this means that a "perfect" shot at 400 is somewhat less effective than a "perfect" shot at 200yds. The bullets are slower and more spread out at 400 yards. This isn't to say that the guns aren't effective at those longer ranges, they're just not quite AS effective, even under "perfect" conditions.
Bullets essentially just poke holes in the other airplane, and that doesn't do much if you don't hit something important (like a spar). Just poking holes in the wing (or fuselage) all over the place won't effect the other plane much. You need to land a concentration of bullets into the correct place, while close enough so that your bullets have enough energy, and for long enough to significantly damage the vital part you're targeting. Placement, energy, and time.
In reality you can't have everything though, so it's a question of "happy mediums" or "best" set-ups, rather than "perfect" set-ups.
Your bullets have the most energy at the moment they leave the muzzle; they begin slowing down right away, so setting convergence in close will maximize bullet energy at impact. Setting convergence in
too close will cause problems though, and make it unlikely that you'll be able to hit anything either closer or further than exactly at convergence (see the linked thread above). Setting convergence out
too far brings dispersion, reduced energy, smaller apparent targets, and increased time-of-flight into the equation (which translates into increased leads and a more-difficult judgement of the speed and flight-path of your opponent), and also leads to some misunderstandings when it comes to trajectory. So, closer is better than further; as long as you don't come in
too close.
What's "too close"? I'd say around 200yds and closer based on what I know when it comes to trajectory. Some of the early-war planes may do well though with a 200-250yd convergence. What's too far? Personally, I think 400 is getting "way out there", but surely 450 is what I'd consider too far. That leaves the space between 250 and 350 to be in what I consider to be the "optimal" range for most weapons when it comes to landing the most rounds possible "on target".
Based on my own shooting preferences, I've settled on 275 as
my best convergence point. I like to begin aiming as I come through the D400 "zone", and solidify my aim to fire just after I close to the D200 mark (which means I'm firing at just under 300 yards whenever possible).
The end result though, is that long-term you'll be more effective on those crossing 200yd shots if you have your convergence set to 200 than you would if you had it set to 400...
