[Kracka]

Use the slave cylinder you are supposed to use (GVR4). If the clutch system is bled properly there is no "space to fill" since it is already full of hydraulic fluid with does not compress (hence why the clutch fork moves). What problem are you trying to fix? Do you not like the clutch engaging 1" off the floor? Depending on how heavy the PP is that may be the best you can get. The extended rod, like shimming the ball, is a band-aid that temporarily solves an existing problem. Ideally, you should have replaced both the ball and fork while the tranny was off, and with a heavy clutch new master/slave cylinders are needed.