Neil -
I'm attaching a PBL that contains a DataWindow/Report that illustrates two similar techniques for producing a solid, colored column background with no gaps when another column uses Autosize Height. The data is saved in the report.
This is how it appears in the preview pane of the DW Painter:
Note: In order for this to work, the column DWObjects have to reside in the Detail band. The technique does not work when they reside in another band, such as a Group Header, because of the way the GetRow() DW function works in an expression for an object that resides in a band other than the Detail band.
Here's the expression used in the Height property:
/* This expression determines the height of each row, which can vary because
the "info" field and detail band are both set to autosize height. It is
CRITICAL that this object's Y-position is Zero in order for the colored
background to be seamless! */
Number(String(Describe("Evaluate('RowHeight()',"+String(GetRow())+")")))
This may not help you in your instance since your columns reside in the Group 1 Header band, but I wanted to show you an alternative that works.
Good luck!