I tried that and it works for this instance, thanks. Is there any way to allow it to have the entire row available to the summary?

There's no property for that, although now that you mention it, it sounds like a great idea. You should Submit a feature request to Infragistics.

The only way to do it right now would be to use a CreationFilter. This would be a fairly simple CreationFilter, assuming you only have one summary. You would have have to expand the SummaryValueUIElement so that it fills it's parent element.

Something like this:

    public class FullLineSummaryCreationFilter : IUIElementCreationFilter
    {
        #region IUIElementCreationFilter Members

        public void AfterCreateChildElements(UIElement parent)
        {
            FreeFormSummaryLineUIElement freeFormSummaryLineUIElement = parent as FreeFormSummaryLineUIElement;
            if (freeFormSummaryLineUIElement != null)
            {
                Debug.Assert(freeFormSummaryLineUIElement.ChildElements.Count == 1, "We are asumming that there is only one summary. This code won't work right if there is more than 1.");
                SummaryValueUIElement summaryValueUIElement = freeFormSummaryLineUIElement.ChildElements[0] as SummaryValueUIElement;
                if (summaryValueUIElement != null)
                {
                    summaryValueUIElement.Rect = parent.RectInsideBorders;
                }
                else
                    Debug.Fail("The child element of the FreeFormSummaryLineUIElement is not a SummaryValueUIElement; unexpected.");
            }
        }

        public bool BeforeCreateChildElements(UIElement parent)
        {
            return false;
        }

        #endregion
    }