I have the design for a bearing that will allow the use of a C body rotor on an B (or A/E/FMJ) spindle. The nice thing about that is the C body rotor is 1.25 thick so the Viper calipers fit without any pad spacers. I'm not sure if I'll ever get any of the bearings made or not though. It costs some money to get a special bearing made even if the modification is easy to do.