Barbette width links guns, protection, and hull strength

Why not make the barbette smaller or wider to solve the design problem?

It must be wide enough for the turret, ammunition handling, and protection, but excessive width can create dangerous stress points in the hull.

A barbette that is too narrow cannot provide enough protected space for the turret machinery and ammunition supply. It must also carry the turret and preserve an armored route for shells and propellant moving upward from the magazines. Making it disproportionately wide creates another problem because the large opening and concentrated loads can put stress on the hull and bulkheads. Barbette diameter is therefore a systems-level compromise among firepower, protection, internal arrangements, and structural continuity.