I'm testing a page for google sitemaps into sitemap module for XOOPS.You can try to install (update) sitemap 1.1 and register XOOPS_URL/modules/sitemap/xml_google.php
I believe it can only help google to crawl your site better (or not). So even if it does work for only 25 % of your site (as example) it still would be a litle beter than noting richt?