Hello George,
only known printed source on this topic is Bagnascos "Le armi delle Navi Italiane". He mentions 8 "idrofoni fissi a scafo sistemati su base circolare" for submarines without any name of vessels. Sounds to me more like KDB-Kristalldrehbasisgeraet. Btw much easier to install than rather sophisticated GHG device. As Perla made it to the well equipped Kriegsmarine facilities at Bordeaux its at least possible.
Kind regards
Markus