Why not arm treaty cruisers with 9.2-inch guns?

Why use 8-inch guns on a larger cruiser instead of 9.2-inch guns?

A 9.2-inch battery would be attractive if the governing treaty allowed that caliber.

The audience asks why an enlarged cruiser should retain 8-inch guns rather than use the Royal Navy's 9.2-inch caliber. A 9.2-inch battery would be a strong option. The decisive constraint is legal rather than technical because the treaty must permit it. Naval architecture begins with the tonnage and caliber rules a signatory is allowed to exploit.