The German riverine flotilla intended for the Danube would have Fluss-Schnell (FS)/Panzer-Motor(PM) boote, armed with 2 3,7 cm armoured cupolas, for which I haven`t found any detailed plans. On the other hand, they would also have an armoured cupola atop the command tower, with two Rheinmetall C/30 2 cm automatic guns. I have found at BA/MA their Solothurn ancestor. Just compare!