Works great on all settings even the lowest. There is a slight difference but it is just that...slight. Theory says it should be less stress on servos, roll faster, etc, etc. You would need an amp/watt meter hooked up to a servo and take readings for each head position.
One thing I will say is that I designed the N5c so that the vertical CG would be right on the boom with the head in the stock position. Moving the head up and down does change the vertical CG.
Have fun tweaking with it, it's part of the hobby!
Matt