If you’re using a BMW master cylinder then you’ll be installing it with the adapter plate supplied by Marlin. This adapter plate leaves a gap between the pin on the servo and the master cylinder. The result is brake pedal that doesn’t work until 1/2 way down.
This is a diagram by a fellow builder – Robin Martin. He had one of these made for me, it just needed a bit fine tuning and edges smoothing off for the final article:
And the result next to a silicon mould of the inside end of the master cylinder:
