The connecting information was the memory of an airforce italian military in Bologna during WWII who told me he saw Stuka passing sometimes in the airport, or maybe based, but he didn't remember more.
Then I read something in
http://www.ww2.dk/oob/bestand/schlacht/bnsgr9.html.
I have a couple of photos token from the ait by british bombers on 23 april 1944, one month about before the arrival of NSG9 aircrafts: the planes look very very little to be recognized, but if you are interested in I will try to report the photoes.
Regards
Toni