Build 3.5.0.133 of xlsgen introduces a new option for using the insert row/col feature.
When new rows are inserted in the middle of an existing spreadsheet, the rows actually propagate the formatting from the row above. This behavior mimics Excel.
In this new build, a new option called InsertFillOption is introduced. It is a boolean and its default value make the insert row/col feature work as explained above. If the option is set to False however, the new blanks remain blank, i.e. the formatting from the row above (or column on the left) isn't propagated.
Of course this option must be set accordingly and before using the insert row/col feature, as in :
workbook.InsertFillOption = False;
worksheet.Rows("5:5").Insert(10);