A few comments, the lift of the slave is:
Slave Lift = Master piston travel * Master Bore^2 / (Slave OD^2 - Slave ID^2)
From the total master travel you have to subtract the distance it takes to close the reservoir bleed hole. The piston travel is determined by the lever clearance to the grip and the distance of the piston pushrod to pivot.
A bleed screw in the top of the slave would make bleeding easier. Otherwise the slave has to be taken out and turned with the hose fitting pointed up to bleed effectively.
There is enough room to include a ball thrust bearing under the large nut or you could also use a small radial bearing to hold the pullrod and have the adjuster nut stop against the piston when lifted like the original. The radial bearing does not take the thrust load, just lets the pullrod spin with the clutch when not lifted.
A Belleville spring curve has a peak if the dimensions are right. The deflection when the clutch is released should be near the rising side of the peak so when lifted the spring load decreases.
The stock clutch dimensions are too far on the rising side for this to happen. You can check this by using a larger master and adding a pressure gauge in the line.