Bernardis was engaged with the construction of several submarines but he also elaborated further the concept of a Submersible cruise with the project of a protected gunship.
The 1927 project has the same hull size but with different shape (coming from real projects).
It was forseen for two twin turrets equipped with 152/50 and the upper part was protected.
Moreover, in order to get more protection, was supposed to operate with two different waterlines: the conventional one for navigation (outside sea) and a reduced one for fighting situations.
It is also interesting to note that was taken into account to use the Ferretti's device which is basically a snorchel developed earlier the the most famous device.
I'll work now on the real submarines between ww1 and ww2 in order to complete the view of the situation.