Tony,
Do the comparison for the OP's alternator stator; not by adding a center tap to it..., or effectively doubling the number of turns in the stator winding as your analysis assumes.
The OP has a fixed number of turns on the stator winding with two wires. He cannot add or subtract turns or add a third wire center tap. 3vO is starting with a fixed AC voltage developed by one given winding.
The only variable he to play with is either using one rectifier or four.
Now rerun your sims with that constraint and see what you get...