The hubs are going to made from Almag 535 which is an aluminum magnesium alloy. It has a very high tensile strength. It machines really well. It's used a lot in the aircraft and medical industry. I do a lot of patterns for a helicopter company and they have everything done in Almag. The nice thing about it is it's right at a T6 hardness with out heat treating. Using castings is going to save a ton of machine time. I'll still machine all surfaces but it will all be finish passes.
I had about a whole day of hogging on the first one I made.
Derek