This is correct. I have the MB CL500 rotors as part of the Stage 4 kit, they fit without any redrilling. I spoke to Cass about that because I like to know what the options are for replacements.
The 13” MB rotor is nicer in that respect than the 13” C4 rotor used with the stage 3 kit, because that rotor has to be redrilled to work (Cass orders blank C4 rotors and has them drilled). The CL500 rotor for the stage 4 kit can be bought off the shelf from anywhere and works out of the box.
Either way the 18’s have much better clearance
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