This is from another forum, and a post from another user, but perhaps it's of use for you or someone in the future:
"The green Bible gives two methods to adjusting the slave pushrod. The 2 7/8 approach OR you can adjust the push rod so that (when the clutch is fully depressed) there is approximately 1/8 in (3mm) of clearance between the bottom of the piston and the circlip at the bottom of the cylinder.
The latter is a better way in my opinion - with different length push rods, clutch plate thicknesses, etc. It gives you a good starting point for the (remaining) life of the clutch plate and ensures the slave cylinder's piston never bottoms out at either end.
The volume of fluid (travel range) moved in the slave cylinder is determined by the master cylinder. All the push rod does is determine where, in the slave cylinder, that fixed travel range takes place. Ideally the bottom of the slave cylinder's piston (when clutch is fully depressed) is as close as possible to the bottom of the slave cylinder without bottoming out. As the clutch plate wears, the bottom of the slave's piston will get a little higher relative to the circlip."