General (naval engineers) Ferrati, based at La Spezia arsenal, was the designer of the first fast battleship class, the four RN Caracciolo. At the USMM (Italian Navy Historic Office) are stored a set of 9 follows on, in three groups, F, D and G, all based on quadruples 381 turrets.
These project can be seen as responses to the current French naval designs (Normandie, Lyon, Gille, Durand A and B).
The D group (five designs) is based on three quadruples 381 towers.
33200 t., 210 l, 25/27k for 65000/85000 HP, 12 381/45 (3*4), 16 152/50 (8*2), 20 102/50 in sigles. Same protection as in F, with indication of displacement variation for each additional cm of armor.
Design D bis:
Same as D, different main towers layout, 12 170/50 (8*2)
One quadruple turret amidship, 12 170/50 (8*2)
with no superimposed quadruples ‘,
as D” but with a significantly lighter secondary: no 170 or 152mm, 28000 t. same speed , reduced HP
(Source: Bollettino d’Archivio, Dic. 1988, A Rastrelli)