Thing is I wanted good memory performance with low voltage. So I tried around and ~1100MHz 5-5-5 was about what I could get with roughly 2.2V. And guess what, due to the low latency and 2T, it was ~1-1.5% slower than 900MHz 4-4-4 1T.
So I kept the 4-4-4 and tried out some sub-timings which gave me another boost of 3.9-4.1%.
1100MHz 5-5-5 2T was as fast (I used SuperPi all the time, 8M and 32M mostly) 900MHz 5-5-5- 1T. As I said, high clocks didn't give me anything on this board. I couldn't run 1T above 900MHz stable, but at least I could run these speeds and 1T with 4 sticks even