They make a mini lite cast vented rotor now. But, thicker minilite OR preferably a standard caliper with 7" thicker rotor is plenty. A Seay Rotor or cast Ripley would be the ultimate upgrade.
I run a BRC 150cc and I put a Ripley on and it had to much braking so I put a 7" old style rotor on and it works perfect now. I only run 1/8 mile tracks.