I didn't change any voltages, just changed from 2133 (which will do 8-10-8-25-1N when I push 1.665v) to 1866 7-9-7-25-1N @ 1.65v. I've switched back to 2133 @ 9-10-9-25-1N 1.65v now though, I discovered 4.7GHz to only be about 98% stable and no amount of tweaking would bring it round. Damn 2500k. 4.6-4.65GHz would probably be stable, but I'm fine with 4.5GHz @ 1.33v.

Model number for the RAM I have is; F3-12800CL7D-4GBRM