With solid cooling we managed to run 3 chip at 91-93 GH/s stable for 3-4 hours.
With our test software and firmware it seems that this is the limit is here.
The strange is that we pushed the voltage up to 0.88 V in order to make it stable .
That's normal, this version of the IC package has about 10% IR drop due to bonding wires used inside the IC, production chips will be better.