From what I understand, and this is from Skuzzy, Pyro or Hitech himself (dont really remember who it was, but it was one of them a hundred years ago) Is the tracing software draws a box around your plane. Fighters small box, bombers big box. It then picks a random spot in that box and if your in the spot, you get hit. Damage model takes over from there and you get a flap damage, or an oil hit, or a smack to knoggin. The big box around bombers is why you dont seem to get hit as often as a fighter, more random spots to be able to avoid.
Yes you can avoid, there is no real trick to it other than not flying strait. Much like running on the deck with an enemy 600 out taking shots at you. Small movement up, down, left and right can make it much hard for the fighter to hit you. Same goes for puffy ack. Keep moving and the tracing software has to keep redrawing the box all over the place. Drop 100 feet, climb banking right, slide left and down, keep moving!
Same goes for field ack a simple porpoise movement (like a kiddy roll a coasted, up and down) is enough to help you avoid getting hit by ack, and manned guns.
Running strait and predictable always makes it easier to get hit.