There's no supported way to do so. By design, there should be no need, however. You turn duplication on for all shares, and even if there's data from your shares on the system drive, there's a copy on another drive as well, so nothing is lost in the event
of reinstallation. You can learn more about data vulnerability if a drive fails from
this FAQ.
I'm not on the WHS team, I just post a lot. :)