How much does a typical modern caliper retract from the disc? Obviously pedal travel is related to this and also includes deflection of the caliper during actuation.

My only input on this is my recent experience with Quick take up calipers and master cylinders VS older types of calipers and master cylinders.The quick take up calipers (also called low drag calipers) retract as much as .030 away from the rotors and require a quick take up master cylinder which is designed to quickly overcome and supply the extra capacity so that on initially applying the brakes the pedal does not go to the floor. I understand these "low drag" calipers came into use in GM products sometime around 1980 as a fuel savings attempt. The older style GM calipers only retract a few thousandths from the rotor and therefore dont have that need for initial "takeup".