For that to use hats? Benefits?

[evilC]

If you use separate bells (hats) and rotors then the advantages are:
1) the bells can be custom made to suit whatever offset you want to locate the brake rotor.
2) it allows you to select different thickness rotors to suit your calipers/application
3) it reduces the heat transfer to the hubs from the rotor
4) You can have fixed, semi-floating or fully floating rotors. Each has different advantages.
5) it is easier to select a custom brake set up as the bells have to be manufactured individually.

Disadvantages:
6) Initial expense
7) You will be confined to using only one manufacturer of rotor for the bell as the number of bolts/bobbins varies between each of them.
8) New rotors and maybe pads are from race suppliers only.