"As I understand it, it's caused by the fork flexing and pulling the brake cable tighter, which in turn pulls the brake pads harder against the rim. I would imagine an alu fork would have to be pretty flimsy to flex that much."
Blimey you guys must have some flex in those forks to alter cable tension!
TBH I thought it was generated by the pads not correctly toed in. They start the judder as they prematurely grip and release (snatch), this gets amplified through play in the cantis and brake bosses, ultimately then violently flexing/juddering the forks.
Can't really see location of cable hanger causing or contributing to the problem