I gave the guns shields because of the rough weather in the baltic and the north sea, I was even thinking of some kind of wether protection (gun indoors a la gun boat, or a fixed turret where you only move the gun)
It is a poor picture but the 2ndary battery is on the gangways, it is only a boat deck hanging over, you can see a similar design in the majestics.
My scale is rather poor but I think it is enough space for the gun crew( loader, and aimer, he also fires the gun, ther is one commander for two guns/ one casemate.