Pivot table exporting to XLSX with posibility to unmerge cells

Hi wizards of Vizlib, 

At the moment we are using the Vizlib Pivot table, thank you for this great extension(!), but we have a/some small extra request(s).

- Export to XLSX if possible with the correct Excel formatting (I see that XLS has some sort of HTML formatting).

When exporting the Vizlib Pivot table to Excel I see that it still exports to XLS instead of XLSX.

Exporting to XLS nowadays leads to annoying security warnings

- When exporting to it should be possible to unmerge cells (perhaps this has something to do with the XLS file or HTML formatting) 

My cells in the parent dimension are merged based on the amount of child dimension values, but I'm not able to unmerge the cells. 

Thank you for your time, 

Kind regards,

Peter