you may have to have it cut while it's still on the wheel carrier. it may warp again in the long run since this is an indication that it is out of true. i've read the techs suggest a good cleaning of the wheel carrier before mounting the rotor to prevent any possibility that something will keep the rotor from mounting straight...
1993 300e-2.8 - gone now <sigh>
"Do not adjust your mind, it's reality that's malfunctioning"