WebDesigner: Column widths on gridBandsWebDesigner

In version 6 you could set the column width in Property Lists per column. This width was used on the GrigBand to line out the columns.
In version 8 (8.0.2) I cannot find a way to define the column width in the property list. How can I define a fixed width (in px or percent) for columns in a PropertyList node or configuration setting of type PropertyList?