Got "Deutsche Flugzeugbewaffnung bis 1945" (German Aircraft Armament until 1945), written by
Manfred Griehl, a good book with regards to the content, but with regards to typos and proof reading
one of the worst I have ... :
There are some information about the Fi 168, too. Intended as communications and ground attack
aircraft, armament is given as 2 to 4 fixed 7.9 mm guns MG 17 and a flexible MG 15 of the same
calibre for the "B-Stand" (rear gunner). Use of the 20 mm MG FF "was principally approved", I suppose
as replacement for the MG 17. If the ground attack version would have had a rear gunner, too, or
the communications aircraft (which seems to have been in direct competition to the Fi 156) only
isn't mentioned unfortunately.