How to copy main site to a sub-site before launch

Hiya!
I know that you cannot use the main site as a NBT. "In previous versions you could" lol

I Wanted to clone my main site before launch, and have it as a template. Any ideas on how i can achieve this now!

I know we have a plugin Paul was working on. The plan was to be able to remove a site from a multisite and make it a stand alone, and add a site to a multisite.

What was the name of that plugin, and has it come far enough to do what i need it to? "Copy main site, and move its clone to a sub-site?"

Thank You!