I am getting the impression that you haven't done your basic research (ie wadding through the vast amount of information in the build logs) the epoxy leveling procedure and rail installation has all been well covered, and Boyan went into this when he started his build. you can't build an accurate machine without certain items(ie precision straight edge and square) no offense is intended by my comments.As Clive has said if you proceed as outlined in the video you will just duplicate any errors in the ally rail.
Regards
Mike