Limit Bandwidth on windows 7 offline files

I am going through testing on offline files.
An issue I am trying to get my head around is how to limit the
bandwidth of the background sync so that it doesn't saturate a slow
wan link, but i still want it to sync back to the source. The
saturation is expected to be heavy on initial role out of windows 7.

offline files sync uses port 445 so i cant really QoS it. I have gone
through the GPO and cant see a way to limit the bandwidth.

I am hoping for a solution that does not include a third party
application.

Any ideas?