Well, our component demands: you do not need to install MS Excel on the server if you will not open the file with MS Excel on the server. And you are right the file should be saved with proper size.
Are you using older Aspose.Excel? and which version you are using? Could you give us info.
And please try to test with the latest Aspose.Cells for .Net downloading it from its download page: http://www.aspose.com/Community/Files/51/aspose.cells/default.aspx
For reference, please check our wiki docs: http://www.aspose.com/Wiki/Default.aspx/Aspose.Cells/
and also the featured demos: http://www.aspose.com/Products/Aspose.Cells/Demos/
Moreover there is not much labor required to upgrade to latest Aspose.Cells (if you are using older Aspose.Excel). Some APIs (classes, struct, enumerations) are added based on some advanced features that we now offer, the previous classes (with their members) are retained and optimised but a few classes are renamed, some additional members (properties, methods etc.) are also included of the classes.
Following is few classes list which are renamed:
1. Excel class is replaced by Workbook class.
2. ExcelDesigner class is replaced by WorkbookDesigner class.
3. ExcelHelper class is replaced by CellsHelper class.