Bob,
Yes, if you reduce the load on the phase conductors, or enlarge the neutral it will suffice. It doesn't remove or mitigate the harmonics, it just gives the circuit a fighting chance from the heat.
Most folks do not do either, so that is why I generally don't permit it.
By the time you get upto the larger switchboards/switchgear, it is not usually needed to enlarge the neutral, as the other loads (of different types) on that larger piece of the distribution system will have "diluted" the harmonic load into a larger capacity equipment.
