Toggling jumping ?

I get the feeling I'm using toggle in a way that it wasn't intended.
This works:

      <div id="show" style='display:none;'>
        <%= button_to_remote "Show", :complete =>
visual_effect( :toggle_appear, "show" ) +
visual_effect( :toggle_appear, "edit" ) +
visual_effect( :toggle_appear, "show_block" ) +
visual_effect( :toggle_appear, "edit_block" ) %>
      </div>

      <div id="edit">
        <%= button_to_remote "Edit", :complete =>
visual_effect( :toggle_appear, "show" ) +
visual_effect( :toggle_appear, "edit" ) +
visual_effect( :toggle_appear, "show_block" ) +
visual_effect( :toggle_appear, "edit_block" ) %>
      </div>

<div id="show_block">
  Show block
</div>
<div id="edit_block" style='display:none;'>
  Edit block
</div>

But the buttons "jump" on the page, as to the blocks. Any idea how to
get one to just replace the other? I've tried setting delay to 0,
e.g. visual_effect( :toggle_appear, "show_block", :delay => 0 )
without luck.

Many TIA,
Craig