What grade for aluminium brake discs?

[cadastrophe]

I want to have new aluminium discs water cut to my own size and pattern, but I do not know what grade of aluminium to use. The maker of the original discs was very guarded, only commenting that I should not use 7076. The discs only see low heat and the pads are Poly Matrix Q ceramic compound.
The discs need to be hard anodized, so the aluminium has to be one of the grades best suited to anodizing.
Has anyone any experience of aluminium discs?

 

[Tmoose]

Hunt and others made plasma faced aluminum rotors for race bikes and maybe cars in the 70s. Under racing conditions the aluminum extruded out like the creme filling in an oreo cookie.

How did your original rotors fail?

 

[cadastrophe]

The originals are still fine after a lot of hard use. I just want to make new discs with a different PCD to fit new aluminium hubs.