I didn't even know Mike was selling this tool, but it is not made in a way that it should be used to final drill the wedge. Only for doing the machine countersinking.
The desire is for the holes to be final drilled perpendicular to the cord
center line. Not one of the sides
This tool is aligning the side
of the wedge square to the chuck (if used in a drill press), so it is fine to use in place of the simple method described in Section 5 of the construction manual, for doing the machine countersinking of the wedge, but not for final drilling.