@ Sam, c7 and c8 working fine here with 1.7v and lazy loose timings:)
http://i.imgur.com/wTvKC1J.png
http://i.imgur.com/xRHxwRD.png
You must have some crazy low voltage dimms if they can do c6 with the above timings at 1.6x volts, as I could not run c6 with the above sub timings with even 1.75v.