The amount of castor (c-hub) to run is a personal choice. At the PanAm race, Desoto Jr (TQ, 2nd) ran 10 deg c-hubs (600303) and Paolo (1st) and Martello (3rd) ran the new 6 deg (600704). Serpent has 0-16 deg c-hubs and its possible to setup your car with all of them. Common new parts run on all 3 cars:
600699
600700
600701
600702
600703
They are all available now and in stock.