I have read that the Canadian squadrons with Halifaxes had a ventral
mounting - not a turret - where a gunner had a good chance of spotting
and shooting at a LW night fighter moving in under him. I also
remember the source cited the RCAF had a much greater survival rate in
their Halifaxes than did the RAF for that very reason. Sorry - I can't
remember the source but believe it was a semi-offical history of the
RAF bombing campaign.
Walt BJ