The Hiyo class began as luxury liners and entered carrier conversion only in 1941, so those ships were not purpose-designed answers to the same prewar requirement. Taiho was more directly related to Shokaku but exchanged aircraft, an elevator, guns, and some speed for greater armour protection and slightly longer range. That package was a different and imperfect compromise, not a straightforward improvement. Shokaku and Zuikaku therefore remained Japan's principal purpose-built prewar fleet carriers.
Notable Point · 41:10-43:15
Hiyo conversions and Taiho's different compromises
Later liner conversions and Taiho altered the Shokaku formula, but did not supply a larger prewar carrier expression of Japanese doctrine.