Not directly an answer to your question, but your biggest braking gains are going to be in more aggressive pads and better fluid.After much googling I've come to ask: Has anyone attempted rear brake upgrades on Golfs with a rear beam? I've seen it mentioned but never confirmed.
Someone called, haha. @bmxdarcy I am running GTI PP brakes on the rear of my Golf TDi. The e-brake lines come in from other side (top or bottom, I forget which) so the e-brake cable routing is shitty, but has not caused any issues since install.