Here is the code I'm working with:

[ 1 ] { flow:south; size: 7,1;} --> { start: south; }
[ 2 ] { size: 1,7; } --> { start: east, 0; }
[ 2a ],[ 2bc ], [ 2c ], [ 2d ]
--> { start:east; end: north,1; }
[ 3 ]{ offset: 0,8; size: 1,7; } --> { start: east, 0; }
[ 3a ], [ 3b ], [ 3c ]
--> { start:east; end: north,1; }
[ 4 ]{offset: 0,8; size: 1,7; } --> { start: east, 0; }
[ 4a ], [ 4b ], [ 4c ]

Which renders this:

+-----------------------------------+
|                 1                 |
+-----------------------------------+
  |
  |                          +---------+                         +---------+
  v                          |         v                         |         v
+---+          +-----+       |  +--------+          +----+       |  +--------+          +----+
|   | -+-----> | 2c  | ------+  |        | -+-----> | 3c | ------+  |        | -+-----> | 4b |
|   |  |       +-----+       |  |        |  |       +----+       |  |        |  |       +----+
|   |  |                     |  |        |  |                    |  |        |  |
|   |  |                     |  |        |  |                    |  |        |  |
|   |  |                     |  |        |  |                    |  |        |  |
|   |  |       +-----+       |  |        |  |       +----+       |  |        |  |       +----+
|   |  +-----> | 2a  | ------+  |        |  +-----> | 3a | ------+  |        |  +-----> | 4a |
|   |  |       +-----+       |  |        |  |       +----+       |  |        |  |       +----+
|   |  |                     |  |        |  |                    |  |        |  |
| 2 |  |                     |  |   3    |  |                    |  |   4    |  |
|   |  |                     |  |        |  |                    |  |        |  |
|   |  |       +-----+       |  |        |  |       +----+       |  |        |  |       +----+
|   |  +-----> | 2bc | ------+  |        |  +-----> | 3b | ------+  |        |  +-----> | 4c |
|   |  |       +-----+       |  |        |          +----+          |        |          +----+
|   |  |                     |  |        |                          |        |
|   |  |                     |  |        |                          |        |
|   |  |                     |  |        |                          |        |
|   |  |       +-----+       |  |        |                          |        |
|   |  +-----> | 2d  | ------+  |        |                          |        |
+---+          +-----+          +--------+                          +--------+

While what I want is something more like this:

+-----------------------------------+
|                 1                 |
+-----------------------------------+
  |
  |                          
  v                         
+---+          +-----+         
|   | -+-----> | 2c  | ------+ 
|   |  |       +-----+       | 
|   |  |                     |
|   |  |                     |
|   |  |                     |
|   |  |       +-----+       |
|   |  +-----> | 2a  | ------+
|   |  |       +-----+       |
|   |  |                     |
| 2 |  |                     |
|   |  |                     |
|   |  |       +-----+       |
|   |  +-----> | 2bc | ------+
|   |  |       +-----+       |
|   |  |                     |
|   |  |                     |
|   |  |                     |
|   |  |       +-----+       |
|   |  +-----> | 2d  | ------+
+---+          +-----+       |
                             |
  +--------------------------+
  |
  |
  v
+---+          +----+
|   | -+-----> | 3c |
|   |  |       +----+
|   |  |       +----+
| 3 |  +-----> | 3a |
|   |  |       +----+
|   |  |       +----+
|   |  +-----> | 3b |
+---+          +----+