Please test the following script:

<verbatim>
pack [panedwindow .pw -width 400 -height 400 -orient vertical]
set a [frame .a -background green]
set b [frame .b -background orange]
.pw add .a
.pw add .b
.pw paneconfigure .a -height 200
.pw paneconfigure .b -height 200
</verbatim>

<p>
Both panes .a and .b are configured with height 200, but .a has height 0, and .b has height 400. This result is unexpected. If I configure the height while adding the panes then it works:

<verbatim>
pack [panedwindow .pw -width 400 -height 400 -orient vertical]
set a [frame .a -background green]
set b [frame .b -background orange]
.pw add .a -height 200
.pw add .b -height 200
</verbatim>

<p>
But the configuring of the panes should also work after the panedwindow has been created.