Mark,

How did the brake duct thing ever work out?

Waiting for the last piece that will close off the air flow so that it's a direct shot at the brakes. Should work very well.

Brake ducts are completed with currently available parts. First review from one member who has taken his M5 to Road Atlanta is that brake fade is gone. He previously boiled his brake fluid on late Fall runs. Will know more this summer when heat really sets in.
What I really want to find next, a version of the M3 Disc cooling part which attaches directly to the hub.
Right now, the M5's have a rock shield in place that prevents most of the air from getting directly to the brake rotors. The M3 version replaces the rock shield and forces air directly onto the rotors. Should provide much more uniform cooling for the rotors.