How to create layouts without duplicated separators?

[nanw1103]

The examples (examples/layout.py, examples/fullscreen.py) creates something like below, with nice borders and titles on each layout:

---t1----- ---t2----
|        | |       |
|   a1   | |  a2   |
|        | |       |
---------- ---------
---t3---------------
|                  |
|   a3             |
|                  |
--------------------

How to create something like below? (Avoid the duplicated borders, but keep the titles)

---t1--------t2------
|         |        |
|   a1    |    a2  |
|         |        |
---t3---------------
|                  |
|   a3             |
|                  |
--------------------

[kehrazy]

Remove the Panel. No border is going to appear.