ADM sell mounting plates for the C8
personally if the intent is for imaging then don't use guide rings go for a fixed mount (less flex)
http://www.admaccessories.com/V_Series_Dovetails.htm
http://www.admaccessories.com/V_Seri...il_Adapter.htm
the 80 tube rings attached to the adaptors then attached this to the dovetail bar atop the C8