Hi Joel,
Try including this flag in the GridResizeToFitOptions, IncludeCellsWithinCoveredRange.
this.gridGroupingControl1.TableDescriptor.AllowCalculateMaxColumnWidth = false;
this.gridGroupingControl1.DataSource = dt;
this.gridGroupingControl1.TableModel.ColWidths.ResizeToFit(GridRangeInfo.Table(),GridResizeToFitOptions.IncludeCellsWithinCoveredRange|GridResizeToFitOptions.IncludeHeaders );
Here is a sample.
GGCResizeTofit.zipBest regards,
Haneef