Not as complicated as you think really, just look at it as 2 x 3 phase setups common output.
The stator was staggered with 2 x 3 phase sets of windings. It was a bit larger.
As we used decent winding wire the regulator was a combination of series and shunt. We didn't have
the problem of insulation breakdown associated with series setups and windings going open circuit
generating huge spikes.