how to select header section in OpenOffice ODT document with TinyButStrong TBS

I can successfully manipulate fields in the header and footer sections of a DOCX document with TinyButStrong (TBS) through this code:

        $TBS->PlugIn(OPENTBS_SELECT_HEADER); 
        $TBS->MergeField('abk', 'ainfo', true);
        $TBS->PlugIn(OPENTBS_SELECT_FOOTER); 
        $TBS->MergeField('abk', 'ainfo', true);

However, this does not work with an ODT file that is just the DOCX file saved in a different format through LibreOffice.

I found out that I can make it work by manually selecting the enclosed file "style.xml", but this seems not the right way to do it as it does not address a document section in the abstract sense:

        $TBS->PlugIn(OPENTBS_SELECT_FILE, 'styles.xml'); 
        $TBS->MergeField('abk', 'ainfo', true);

Does anybody have a better solution?

$TBS->PlugIn(OPENTBS_SELECT_FILE, 'word/header2.xml', false);
$TBS->MergeField('abk', 'ainfo', true);