Using 3rd party sitemap generator w/VBSEO sitemap

For quite some time, I have been using vbSEO sitemap generator. This has been great for my forums, but I want to start submitting my site's sitemap to Google. I have a 3rd party app that is generating a complete sitemap (including forums). I'm guessing the vBSEO sitemap does some things with regards to priority,that makes it worthwhile to keep using it for the forums.

Is there a way to use both tools? In Google Webmaster Tools, I have verified my main site, but I haven't shown it the new sitemap. I haven't verified the forums, but I do submit the sitemap file daily.

Any suggestions on the best practices for using Google Sitemaps is apperciated.

Thanks.

If you can have your 3rd party tool write to the extra-urls.txt file that exists in the vbseo_sitemap directory, vBSEO Sitemap will merge those into it's sitemap files.