Infinite SEO: Sitemap.xml Specify Mapped Domain Name?

I am running WP 3.3. multisite using subdomains.

mydomain.com
site1.mydomain.com domain mapped to site1.com
site2.mydomain.com domain mapped to site2.com
site3.mydomain.com domain mapped to site4.com
site4.mydomain.com domain mapped to site4.com
ETC.

I am using wpmu-dev-seo (https://premium.wpmudev.org/project/wpmu-dev-seo) to automatically generate sitemaps for all my websites which works well.

However, when I view the XML sitemap for some websites, the URL which appears is the subdomain (site1.mydomain.com). When I view the XML sitemap for other websites, the URL which appears is the mapped domain (site1.com).

How can I ensure that the sitemap.xml file always uses the mapped domain, and not the subdomain?