How to change the font size for header with ColumnSizer as SizeToHeader in WPF DataGrid (SfDataGrid)?

this.DataGrid.GridColumnSizer = new GridColumnSizerExt(DataGrid);public class GridColumnSizerExt : GridColumnSizer
{
 
    public GridColumnSizerExt(SfDataGrid dataGrid)
        : base(dataGrid)
    {
 
    }
 
    protected override FormattedText GetFormattedText(GridColumn column, object record, string displayText)
    {
        var formattedText = base.GetFormattedText(column, record, displayText);
 
        if (record == null)
        {
            formattedText.SetFontSize(16);
        }
        return formattedText;
    }
}