I found this video recently. It details how the Luftwaffe formed attacks on flights of B-17's during the Defense of the Reich phase of the air war. Unfortunately, the best method seems to have been an initial head on attack. I say unfortunately because the way AI are programmed in CFS2 we can not implement this into our missions. They will fire a short burst head on if they are kept in formation straight towards the bombers and are then told to attack. But after that they always assume a six o'clock attack position for the remainder of the engagement.

Still, it's an interesting video that covers not only the tactical practicality of this attack but also the reasons why it was psychologically effective for Luftwaffe pilots to attack head on grouped close together. https://www.youtube.com/watch?v=KO4B4-DvS-o&t=2s