Three triple turrets can provide more firepower than four twin mounts while using fewer turret positions and less deck space. Those savings matter especially in a battlecruiser, where the machinery needed for speed already dominates the design. The remaining hull still has to accommodate that machinery, protection, and secondary armament. Reducing the number of turret positions gives the designer more room to arrange those competing demands. The triple mount's value here comes from the balance it permits across the whole ship.
Chapter · 22:17-23:09
Deck space and the value of triple turrets
Triple mounts can save turret and deck space, a particularly valuable advantage on a hull already crowded by machinery for high speed.