South Dakota's guns and the cost of naval tradeoffs

What sacrifices did the US Navy make to carry nine 16-inch guns in the South Dakota and North Carolina classes?

Protection was among the tradeoffs; designers used layout and angling to compensate, but displacement could not maximize guns, speed, and armour together.

Protection is identified as a cost of fitting nine 16-inch guns into the South Dakota and North Carolina designs. The earlier guide's comparison with Texas supplies the example: its printed deck-armour figure is thicker for the older ship. Angling the protection is described as one way to compensate. No full armour scheme or quantified tradeoff is supplied.