In article , The
Enlightenment writes
However I still suspect that a simple rear gunner lieing in the prone
position could be built not to reduce speed too much.

I guess it puts a lot of weight (the gunner) very far back, which would
probably have large effects on handling. Just fixed guns with lots of
tracer might be effective, especially as a tail chase was quite likely.

The ultimate gunnery system in WWII, particularly for night ops was
probably the radar guided system used on some Lancasters (Village Inn
perhaps?). Whether this could have been incorporated into a small tail
turret remotely controlled from the cockpit is another question.

--
John