Got an email reply, here it is:
James,
Yes we do sell a rotor that is 5mm in size for the C50 Maxx motor. The C50 L rotor will not work with the C50 Maxx motor for it has a special magnet length.
The 5MM rotor would be $75
Best Regards,
Kyle Bergstrom
Aero-Model/Hackerbrushless USA
Repair Dept. Manager
www.hackerbrushless.com
www.Aero-Model.com
2122 W. 5TH PL.
Tempe AZ 85281