On proper PCB such as on Ballistix, Micron D9PFJ can scale well up to 2.1V and do 900MHz/6-7-7, 1066MHz/7-8-8 (on 4Gb modules) and 1200MHz/8-8-8 (on 2Gb modules).
In my case, the issue was that 4Gb sticks couldn't do over 1100MHz no matter what, 2Gb modules also had issues above 1200.

The newer stuff seems a lot better as there are people who did 1066MHz/8-8-8 and 1200MHz/9-9-9 at 1.65V with 4Gb sticks, but I'm not sure if those use the same Micron D9PFJ's.