Easy -
Make CV's invulnerable to .303s, .50s, 20mm, 30mm, 37mm, 40mm rounds.
After all, as if even a 40mm round would worry the cruisers main guns, or for that fact the 5"ers.
Most CVs are sunk after they have had their guns killed by suicide 110's etc, then someone pops in with some eggs to finish it off.