ALV with Excel inplace: font size in excel template does not apply

We want to display an ALV list of a standard SAP report with a bigger font. To achieve this, we thought of using the excel in-place and adjust the font size in a custom excel template.

So I created a customer template excel file and set the font size of all cells in the sheet "format" (the first sheet in the template) to 14. I then applied this template with the output of transaction IW38.

Strangely the font displayed in the in-place excel is still 10, not 14 as I suggested. Where did I go wrong?