I finally stumbled on to the centering and maintenance of poetry formatting.
The "centerbox" tag does the trick.
<div class="centerbox">
<div class="stanza">
<span class="i0">Mi memoria en ti se ocupa</span><br />
<span class="i0">No te olvida un solo instante,</span><br />
<span class="i0">Y mi mente delirante En ti piensa,</span><br />
<span class="i0">en ti piensa sin cesar.</span><br />
</div>
</div>