The system was running beta firmware which provided access to AirCRM cloud control. Theoretically this meant that I could monitor the system remotely. Unfortunately it was far from stable in the sense that antennas showed as "offline" often and I couldn't do anything usefull remotely. The development of the firmware has currently been halted because ubiquiti's priorities have changed. So I decided to install the latest official firmware release (V7.1.4) for the AirMax AC antennas and see if it would bring any positive changes.
And behold. Throughput has gone up from 35Mbps to 45/50Mbps. Can't complain about that.
George Timmermans, Research Toolmaker, Software Engineer and Tinkerer