[Junket]

My experience On the slave slave you need 1-1 you are displacing equal parts fluid and you don't need a lever factor, you don't want to displace more on the slave (blow the O rings) on the mulit-disk they don't need to move as far as a single you can go under on the MC there. As far as the brake you you are not displacing the the full piston on the calipers just moving the puck a little that is where the lever factor comes in with the diameter of the MC. come in to play.
Ken