As folks know I tend to run most applications maximized This is easy with some and hard with others Gimp 2.6 with it's multiple windows is one.
After a bit of searching and tweaking and using xprop I have it working as I need.
My rc.xml has this
<!-- gimp toolbox-->
<application class="Gimp" name="gimp" role="gimp-toolbox" type="utility">
<decor>yes</decor>
<maximized>false</maximized>
<height>50%</height>
<fullscreen>no</fullscreen>
<skip_taskbar>no</skip_taskbar>
<skip_pager>no</skip_pager>
<position force="yes">
<x>0</x>
<y>0</y>
</position>
</application>
<!-- gimp dock--><!-- "Layers, Channels, Paths, Undo - Brushes, Patterns, Gradients"-->
<application class="Gimp" name="gimp" role="gimp-dock" type="utility">
<skip_taskbar>no</skip_taskbar>
<skip_pager>no</skip_pager>
<decor>yes</decor>
<maximized>false</maximized>
<height>50%</height>
<layer>default</layer>
<position force="yes">
<x>-0</x>
<y>0</y>
</position>
</application>
<!-- gimp image window-->
<application class="Gimp" name="gimp" role="gimp-image-window" type="normal">
<decor>yes</decor>
<maximized>false</maximized>
<placement>
<policy>Smart</policy>
<center>yes</center>
</placement>
<position force="yes">
<x>center</x>
<y>center</y>
<height>50%</height>
</position>
</application>
<!-- gimp layer new-->
<application class="Gimp" name="gimp" role="gimp-layer-new" type="dialog">
<decor>yes</decor>
<maximized>false</maximized>
<height>50%</height>
<skip_taskbar>no</skip_taskbar>
<skip_pager>no</skip_pager>
</application>
Work in progress but looking good