The Southbend disk is approx 20 thousands thicker than an ACT disk, PERIOD !
And if I may finish Reza's quote you need that much more "Trow" to disnegage the Clutch.
I'd say Bleed it the good old way then have a good look at the position of the Fork inside the Window.
If all fine; replace the Master and Slave and if that does not cure your problems then replace the Fork and Pivot Ball as well as shimming the Ball as required.
Ghislain
