Posted for "Richard Freilich" <rfreilich@sbcglobal.net>:

 Not that I am an expert in these matters, but would have drilled the holes
 angled in the direction of airflow and rotation.  This provides more surface
 area
 
 to be cooled and increases airflow.  This what my Suburban slotted and
 drilled front discs had.
 
 
 
 Richard Freilich