A twin 5.5-inch secondary battery for Renown

Would Renown be better with 5.5-inch guns, and how many could she carry?

Yes; about six twin 5.5-inch mounts would provide a practical replacement battery.

The estimate starts from the historical positions of Renown's two single and five triple 4-inch mounts. A 5.5-inch weapon offers a heavier and more useful secondary shell, but the new twin mount requires careful placement. Six twin mounts fit comfortably, while seven might be possible at the edge of the layout. The more credible modernization is therefore twelve 5.5-inch guns in six twins rather than simply multiplying mount count.