Permit overlapping edges in graphviz

Question

Background

Use graphviz to create an Organizational Chart.

Problem

By default dot creates the following diagram:

The desired output combines the edges so that they overlap, with elbow connections:

Source Code

The following source code generates the problematic diagram:

digraph G {
  splines = ortho;
  concentrate = true;

  node [shape="box", style="rounded", penwidth = 2];
  edge [color="#142b30", arrowhead="vee", penwidth = 2];

  {
    rank = same
    "1";
    "2";
    "3";
    "4";
  }

  "Main Node" -> "1";
  "Main Node" -> "2";
  "Main Node" -> "3";
  "Main Node" -> "4";

  {
    rank = same
    "5";
    "6";
    "7";
  }

  "1" -> "5";
  "1" -> "6";
  "1" -> "7";
}

Question

How can dot create orthogonal, elbow-joint edges in a Manhattan layout?

Ideas

I have tried various combinations of sametail and tailport to no avail.