Dear Clegg,
Need to check to be sure, but I think the restrictions on the 沪C plate relate to the Inner Ring, not the Middle or Outer Ring. Every day I pass under Zhongshan North Road, i.e., the Inner Ring, and there's a sign saying no 沪C or 沪B plates beyond that point. Didn't you say you were outside the Inner Ring?
Guy to ask would be Dewsnap, who currently rides under the 沪C banner.
Wonder whether there's a friendly email answer line like the one Lao Jia Huo discovered in Beijing...
Yes, Taobao can be a wonderous thing!
cheers