I agree with Larry, I've never had a rotor warp, and I wonder if the rotors we're buying are of a lesser quality. BMW (USA cars) for several years have had a problem with warp rotors, which seems to stem from poor material quality of the rotors, not size. Another reason causing rotors to warp is from a dirty wheel mounting area, such as rust. If there is any areas of uneven rust, the wheel will not torque evenly, leading to warpped rotors.
Suginami if you can use the larger rotors, as you know improving the mass, less problems with heat and cooling.
Enjoy your drive, timreid
500E sway bars
210 16in wheels