Charybdis,
I believe that your 5"/25s are too big. NavWeaps gives the oal gun length as 142.25" roughly 12' in SB scale.
Dave
nope, the gun is 142.25in that is 3.613 meters
3.613 meters * 2 / 0.3048 = 23.7 meters.
or on the other hand, those guns was drawn from blueprints... if I'm correct.