# Soften the sharp edges
    fillet(holder.edges().filter_by(Axis.Y).sort_by(Axis.X)[2:4], lip / 3)
    chamfer(holder.edges().filter_by_position(Axis.X, 1, size.X), 1 * MM)

    # Create the mounting screw hole
    with Locations(holder.faces().group_by(SortBy.AREA)[-1].sort_by(Axis.Y)[-1]):
        h = CounterSinkHole(3.8 * MM / 2, 7 * MM / 2)

    # Mirror to complete the part
    mirror(about=Plane.YZ)

    # Create a centered alignment notch to help with mounting
    min_z = holder.part.bounding_box().min.Z
    with Locations((0, -thickness, min_z)):
        Box(
            sqrt(2),
            thickness,
            sqrt(2),
            rotation=(0, 45, 0),
            align=(Align.CENTER, Align.MIN, Align.CENTER),
            mode=Mode.SUBTRACT,
        )

holder.part.export_step("holder-212.step")
print(f"Mounting holes spacing: {2*h.center().X:0.1f}mm")
show(holder)