I'll invite you to take a look at my epub-formatted book. The 9th section called "Tarot" (adversary) is a collection of poetry. In particular, numbers 19, 20, 22 should prove good examples of a "best-fit" solution. Due to page-width, it's really a matter of doing some "padding-left" and "padding-right" work... coupled with some left, right, or center, alignment... Also, because you don't want stanzas breaking across pages (and when the user selects large size fonts, they will), I made sure to use ".dontbreak { page-break-inside: avoid ; }" in the CSS as well...
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