i saw something here on sitemap_index.xml.gz i thing this could not harm but i should tell you about it:
<?xml version='1.0' encoding='UTF-8'?>
<sitemapindex xmlns="http://www.google.com/schemas/sitemap/0.84"
xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
xsi:schemaLocation="http://www.google.com/schemas/sitemap/0.84
http://http://www.google.com/schemas/sitemap/0.84/siteindex.xsd">
<sitemap>http://forums.example.com/sitemap_1.xml.gz</sitemap>
</sitemapindex>
look at the BOLD text
and you check it tell me if it is only me.