I use the 400 200 on cannons and 400 400 on MGs as per the Luftwaffe diagram. Like Tom said with the cannons they are fairley inaccurate and so for this reason I only use them for close range, like 100 metres on small targets like fighters. I also like to save ammo and confirm I am going to hit by using the MG's to draw on to the target and when you see hits fire the big guns... Tracers and or Beobachtung are good for this.
Firing on fighters dead 6 is kinda wasteful, the low volocity cannon rounds tend to go over and under the wings of your target as the wings are so thin from this angle. In fact from dead 6 you are better using the nose MG's to aim for the oil cooler or water rad as this will be just as crippling as a hole in the wing... Firing straight down the fusalage is largely wasteful.
The best target I feel for a fighter is 90 degree on top on from below as he turns. You often have to draw blind lead under your nose and experieced red pilots will add slip with the rudder so expect to miss sometimes. How ever the window for shooting is smaller so you use less ammo and the target is bigger so you have more chance of a hit. Ideally these shots are at less than 100 metres, wingspan of target fighter once in your recticle, you have to get close.
I had cannons for a long time set to 100metres however this only limits your options should you need to fire them at longer distance... Like to scare someone off your wingman. The cannon trails have a good phycological effect...
I'd really love to try a 109 with 8 wing MG's like the hurri set up just to see what its like...
Just my 2 cents, as always...
