You can set it either way.

Power output of each person should remain the same, so phase has no impact on power. It just feels more smooth for us, or I would probably be totally in phase. 90 degrees off or some other drastically different angle i haven't tried but it should reduce the pulsing of power especially on hills which would feel faster and it very well could be faster as well since you don't get a chance to surge in speed (though small surges) and have micro accelerations with the bursts of power to the wheel.


We don't use power meters but it would be interesting to hear of these tests. Powertap pm+two garmin power meter sets would be able to tell what's fastest.