How tight does the rotor and the spacer fit to the hub? I'm thinking that the spacer might be a tighter fit, and is bolted to the rotor to make it hub centric. On the original application of the rotor, the studs were pressed in the behind the rotor and into the hub, which would center it. Since it mounts from the front in this application, the center bore may not be tight enough to allow for proper centering.
