I believe the Lufwaffe tested all these Italian fighters with a view to possibly producing them in conjunction with the Bf109, of even replacing it. The rationale was that the small airframe of the 109 was unable to take full advantage of the the increasing power of the avilable enginves. The Centuro and Veltro were rated as very good, the Saggitario excellent. At the end of the day it was the long construction time that made the Luftwaffe stick with the Gustav even though they realised the 109 was pretty much at the end of its design life.