Customising (Customizing) Subgroup Home Page

I'm very frustrated that I can't add modules to the Subgroups Home page. I know I can use the HTML option in the Content area to add a widget, but this is not what I need. I need to be able to add the Groupsite Newsfeeds module to the Subgroup Home page.

Without this flexibility - one of the great attractions of other parts of the Groupsite framework - I'm not sure I can achieve my objectives with the site I'm developing.