I sold that miner but I'm going to do the same thing again soon to a S7 when the S9 arrives and I rearrange my miners and PSUs.
Here is my setup:
Power supply: Enermax Revolution 87+ 1000W
Voltage: 227 VAC
Current: 4,7 A
Power (at wall): 1066,9 W
So that is 1067W/4223GH. Or 0.252w/GH. You obviously lowered the watt draw, but I'm confused as to whether you are running more efficient as s7 is rated at .25J/GH, right?
The consumption in 12VDC side is maybe something like 0.88x1067W =938.96W (I used 0.88, since it is 87+ efficiency PSU with almost 100% load)
And the efficiency for S7 is then about 0.222.. J/GH.
The number Bitmain gives for the miner efficiency doesn't take the PSU into account (power at wall -efficiency).
I'm getting the most hash out with the Enermax PSU by using these settings.
With 650Mhz frequency the load is too much for this PSU and it occassionally turns off.