Hi again Jeroen
It was
Koflak 11 which was stationed in Macedonia together with
Koluft 11and and Kofl 11. (also AFP 11)
Not entirely sure but think all units were stationed at ûsküb (at least partly)...!?
I have
Hptm Herbert Schumann as Koflak 11 until spring 1918, dont knew when he took command...
Roughly I think Koflak 11 might have consisted of 10 to 20 Flak units...
It might be possible to find order of battles for 11th Army in some military books/works and also in Freiburg archive...
Hope it helps little

Gunnar