Hmmmm - the thicker the clutch plate, then the further out the release bearing will sit, so the push rod will be back further back. So as the slave starts to move, the clutch will be disengaged and then lots of travel still to go because the slave is starting from the beginning of it's possible travel (sounds like what you have). The problem with this scenario is that when the plate does wear, it will try and push back into the slave further, but it can't because it's already fully in, then it will always be acting on the release bearing slightly (not good for it) and eventually it won't let it come back far enough so the clutch will always be slightly disengaged and it will slip.
When it's worn and thin, the bearing moves in and the push rod will sit further out. Once it bites it will not have a lot of travel after it because the slave will be starting from a further out position.
If the clutch pedal and all the rods are properly set then the pedal should actually start to actuate a new or worn clutch at about the same point (hydraulic clutches are self adjusting).
So, you could, shim the slave out a bit (there are shims available). So that there is a bit of slack before it disengages the clutch.
Yours is only biting near the top, so it could be that the push rod on the master and or the pedal is not allowing the master to come fully out.
