[Zope-CMF] Portal Customization question

[Chris Keating]

<dtml-with portal_properties>&dtml-title;</dtml-with
   ><dtml-if name="Title">: &dtml-Title;</dtml-if>

Without changing every DTML instance that resembles the snippet from
above, how can I define a title for the CMF site's index_html such that I
no longer have a CMF Site that reads
"portal_properties.title:portal_properties.title" ?

I tried to customize index_html and change the title, but the value wasn't
acquired.