The only way to diagnose and correct the clutch engagement point is to mechanically diagnose the system. If the clutch is engaging to "late", and the master cylinder is not overfilled, then there is a mechanical reason. I would first measure (with a dial indicator) the amount of clutch plate lift - the amount of push rod travel you get when you squeeze the clutch lever. All things being as designed, the pushrod is designed to travel .065" when you squeeze the clutch lever. If you have less than .065", you likely have air in the system. (Air in the system would result in the clutch engaging to soon rather than to late, or not releasing at all.) In my experience typical pushrod movement in a properly bled system is .065" to .073". If you have the proper amount of pushrod movement, then your master cylinder and slave cylinder are functioning as designed. If you have the proper amount of travel, yet the clutch engaging "late", then either the pushrod is to long (with a 6 speed transmission, the push rod should be 15.552" long), the clutch plates are to thin, or there is another mechanical deficiency. It could be bent snap rings in the release plate assembly causing the issue. But rest assured, if you have the proper amount of clutch plate lift, something mechanical in the release mechanism or clutch hub assembly is either damaged, worn or was manufactured out of tolerance, causing the clutch lever to engage the clutch mechanism to late.