The planned destroyer combined sonar, mine-laying, depth charges, and five 135 mm guns. Removing the aft Y mounting would have created more room for anti-submarine equipment, but it would also have reduced the firepower available for fleet screening. A hypothetical three-twin arrangement could have supplied six guns while freeing two single-gun positions. That arrangement would have required development of a new twin mounting during wartime. The five-single proposal avoided that extra development, while the alternative promised more room for anti-submarine stores.
Chapter · 33:03-34:27
Gunpower versus anti-submarine capacity
Five single 135 mm guns preserved screening firepower, while twin mounts could have freed more deck space for anti-submarine stores.