I tested a bunch of different settings; I recommend:
Fan % Freq Watts TH/s Error %
30 612 1237 4.85 0.025
Measured 76 dB at 30% fan speed; surprisingly quiet.
These run about 5C cooler than an S5+ 1/3 with the same power consumption.
This allows you to run the fan at a lower speed.
I used an EVGA 1300 G2 PSU so you should get slightly better w/GH with a server PSU.
0.255 w/GH with a Gold PSU

cool...I will be running mine at a "fullzero"TM settings first.