How to use old (screen) style splits

A quick update C-a ? reveals that C-a % does the vertical split. This is, however, still the odd split behavior I mentioned in my original question.

Note that in Byobu, you can also use:
 - shift-f2 for a horizontal split
 - ctrl-f2 for a vertical split

I understand how to make the splits, but I am more interested in how to switch between terminals as was possible in the old version. It used to be that I could have window 0 in one part of the split and window 3 in another and it was easy to switch which window existed in which part of the split. Is this still possible?

I just wanted to add to this. I've discovered that it is possible to take two windows and combine them into one (with two panes) using the C-a :join-pane -s <src> -t <dest> command. The break-pane command will allow you to get things back to two windows. This will allow a work flow similar to byobu's screen days, however, it still provides no easy way to switch between what window appears in the pane.

An example of how I used to use this:

1. Split screen into two panes.
2. Run irssi on the top pane
3. Use the bottom pane for tasks I was doing, this could span several additional Windows as commands like C-a n and C-a # allowed you to swap the bottom pane with any other windows.

If there is any way to reproduce the above easy pane switching, I'd love to know it.

    Alt-F11                     Expand split to a full window
    Shift-F11                   Join window into a horizontal split
    Ctrl-F11                    Join window into a vertical split
    Ctrl-F3/F4 Move a split

This seems to result from the switching of byobu from gnu-screen to tmux (as the default backend).

If you'd like to have the old behaviour again run:
     byobu-screen
or switch the backend using
    byobu-select-backend

tested on ubuntu 12.04 and 12.10