Hello all, first of all I love this plugin and I use it on all my wordpress websites however I never use the sitemap feature for various reasons. If you need to implement a sitemap quickly, don't use the sitemap function in the plugin and installed Google XML sitemap plugin.
I know this does not answer your question but at least you would have the best of both world. WordPress SEO by Yoast plugin and Google XML Sitemap.
Kind regards