Build 3.0.0.159 of xlsgen writes chart-level font formatting for XLSX charts. This has an effect to all chart elements with no font formatting. For instance, if the chart-level font has a font with size 8, the legend will also be displayed with a font with size 8 unless there is a custom formatting at the legend level.

Those chart-level font formatting details were written for XLS charts, but not yet for XLSX charts. Until this build, that is.