We now have a potentially interesting new development on this issue!
It seems that a couple of 5 kW units are achieving higher max output capacities if the pump speed is set to max rather than auto.
Note in particular these two tests on two different systems with flow rates at 22-24 L/min:
The outputs are substantially higher than most of the other tests, that have system flow rates of 12-14 L/min. It’s not always consistent e.g the 18.9 L/min test that only achieved ~4.9 kW
Two systems is not enough to be conclusive, it would be great to have some help to verify if this pump settings makes any difference for others at the limit with their 5 and 7 kW Arotherms this winter!