Howdy Seeker,
Utilising the older 6" in that way is quite possible. If using in shields on a BB/BC I would point you to the layout the Hood used for its secondaries. For cruisers you need the extension to the deck above that helps shield the gun below from the blast of the mounting above.
Both the Italians and British spent money refurbishing their 12" (to 12.6") and 15" respectively, trying to achieve longer range and/or firing heavier shells in the Italians case.
I have included a pic of a 6" triple being fitted to UK cruiser which shows the various bits of the workings that go inside the barbette.