The ends belt is there to sim the protective boxes (all four sides) around the main rudder room and the auxiliary rudder room (using an average thickness of 14") so I would assume it is a little bit more than that.
I only used those boats as a base. I took the data and made minor changes to them so the three designs are slightly different from the actual G 5, ¦ 4 and MAS 501, not copies. Kind of like my Type 96 medium tank.