I'm going to speak heresy:
Your convergencies (and joystick settings) do not matter.
OK- that's not quite true especially with respect to AC with multiple MGs and no cannons, but what I mean is that more important than any particular settings is practicing and getting familiar with one set of convergencies that suit your type of gunnery.
In my case, I tend not to suscribe to the "wait 'til you see the white of his eyes" technique- if that is yours, then with multiple low calibre MGs you probably want convergencies around 100-200.
If you're like me and you tend to take many high-deflection and long range pot-shots (from as far as 700) then you are probably well-served with choosing convergencies of around 300 and practicing and practicing and practicing until you get a feel for where the rounds go.
Having that higher convergence gives, I think, a bit more spread in your cone of fire and increases the chance of getting "lucky" hits of attriotion rather than a moment of kablooie instant destruction.
One final comment, hub/center mounted cannons can be set to quite high convergence (say 700) as this affects the "lob" of the rounds rather than the "centering" of the rounds; having a high convergence therefore makes deflection shots in turns easier as the rounds at targets at distances of less than 700 (if that's your setting) will go "above" (ie: more into the turn) the pipper.
Again though, in my view, the specific convergence you choose if you are going to be shooting from any position other than from behind at short range doesn't really matter; far more important is practicing with only one convergence (with one AC as it changes with each different fighter) and getting to "know" where your rounds will go.
My 2cents....
Cheers,
C_G