In books I've read about the Bomber force comments are often made that crews were told the German's had scarecrow shells - to mimic falling bombers to scare crews...
I've asked before on PP about Schräge Musik & why crews were not warned nor ventral guns not fitted. On that thread some soul posted images of ventral turrets that were fitted (IIRC mostly Canadian squadrons??).
There have been comments to that Harris wanted to be sure each bomber could carry the maximum amount of bombs on any given operation & thus he wanted the save as much weight as possible.
In hindsight simply having a force half with upper turrets & half with ventral turrets - would mean approaching night fighters would have something to think about.
IF it was officially known Schräge Musik was really bringing down most bombers..?
Edited to add:
http://www.pprune.org/aviation-histo...age-musik.html