[qubes-users] updates-only standalonevm

I made a standalonevm based on the default fedora-18-x64 template. I want no networking for this VM except yum updates (just like a templatevm). So, I set firewallvm as its NetVM, and under Firewall Rules, I set "Deny network access except..." and checked "Allow connections to Updates Proxy." I did not add any custom firewall rules. (In other words, everything exactly like a templatevm). However, it cannot reach the update server. Is there a way to do this?

You need to additionally add service 'yum-proxy-setup' in "Services" tab. This
will configure yum to actually use the proxy.

Thank you.