As a genral rule I would say you should have a small amount of play on the rotor(about .1-.2mm) cause if you have no play it means the rotor is 'nipped' between the two bearings, all the novaks I've used only have 1 shim, but if you have loads of play with 1 shim in I would put more in but put them at the sensor end just incase the rotor is close to them
