Thanks! Great to hear it’s working for you.
The version of Fedora used in the Vagrant container image should preferably match your base Fedora version, so the versions of libvirt inside/outside the container match up.
I’ve done a quick update of the vagrant box building image so it will use the stable stream by default. The box name is also changed from fedora-coreos-preview to fedora-coreos.
With this stable release I should really get back at testing FCOS myself again…