short answer: you can't, really.
The thing is: CW panels can have
form, not just rectangular.
You should look into the guide of GS: "How to create a CW panel?
There is a very helpful illustration of all the parameters you need for scripting your own panel
Also it's helpful to open the panels which come OOTB in the GDL editor and look how they are made.
I have also made mods
to the ones from GS.