Hi Dave,
I’ll have to check if there’s been any other mods other that the twin reservoir master.
Initially it was holding pressure all the time, rock hard peddle after a few applications, brakes red hot. He opened up the master and removed this (see pic).
Following that is seemed ok, now it’s started doing it again. A short drive to the local servo with half a dozen brake applications, the fronts could not be turned by hand and were red hot. After 30mins you could doing them half a turn.
Front calipers have been tested and they moved freely.