After seeing that thread about the pro driver that raced a full season with a WRX 4-pot/2-pot set up big brakes have lost their luster, to me.
Litchfield Imports uses them on there Type25 on the fronts. But I agree the 4/2 pots would be more than enough. Also I have been told alot of the pro rally guys ran 4/2's on the gravel, may even still I'm not sure. Cool rally car link http://rally.subaru.com/rallycarexplorer.html
Actually, I just found out that the Porsche 6 pots bolt on to the bracket from the Brembo Grand Turismo BBK and use the same rotor...