This is the only reference on the subject that i can find right now. The pertinent section is at the bottom.
The following U.S. intelligence report on evasive tactics of Luftwaffe bombers was published in Tactical and Technical Trends, No. 16, Jan. 14, 1943.
Thanks Robert. Seems my theory was wrong. Story of my life
Having said that I will come up with another quick story. And that is the violent manouevre called the "Corkscrew" used by British bombers as a means of evading fighter attacks. I could never quite understand why this was used as for a few moments in the manoeuvre as the bomber reverses its direction of turn it is a sitting duck. We used to practice fighter affiliation between Lincolns and Mustangs and I flew both.
A few years ago at an Aviation Historical Society meeting in Melbourne the guest speaker was Tony Gaze a Spitfire pilot with 14 enemy aircraft to his credit. When asked about the practicality of the Corkscrew manoeuvre used by Bomber Command crews, he said he could never understand why this manoeuvre was used as it was so easy to shoot down the bomber as it reversed its turn. He had told the various RAF staff concerned with tactics that the Corkscrew manoeuvre had probably caused the destruction of many bombers. But apparently nothing was changed. Although it is hard to know what else the bomber crews could do when attacked. De-syncronise their engines, perhaps