Copper is also 60% better in the thermal conductivity properties as well, which is another critical property.

Power density in an electric motor is really based on how fast you can remove heat from the motor. I'm involved in sizing industrial servomotors, but even there you have 1s/10s/60s power ratings.

I wonder if H3X can post higher power levels for takeoff, assuming it starts cold and the flight plan calls for throttling back after a certain altitude is reached. And even in the event of an immediate 150% power return to runway after a 150% takeoff, the motor might only have slightly degraded the winding insulation; it can almost certainly exceed its ratings once for long enough to get back to the ground.