[JSeery]

My guess is they can use the larger diameter master cylinder because the brake pedal is designed with more mechanical leverage. The larger the MC dia the lower the line pressure for a given pedal force (leg force). This can be overcome with a larger pedal ratio. This is somewhat difficult to do in a car because of space constraints, easier in a truck (more room). The only real advantage to a larger dia MC is it moves more fluid volume for a given amount of pedal travel.