13/16 slave
5/8 master cylinder

i'm noticing that with that setup it's actually harder to press the clutch in than it should be. normally the master cyl is equal or larger in size, otherwise the mechanical advantage is reduced below an efficiency of 1:1

What you have is a clutch pedal that requires 1/3 more pressure than it delivers
so you push 1.3 lbs on the pedal and the slave only produces 1 lb of force.