Hi Matthias,
Thanks for your update.
We deeply regret for inconvenience caused.
We are unable to reproduce the issue which was mentioned by you in the last response of this forum(legend font size not working properly in some cases).
We suggest you to use RepresentationType property of legend to customize the icon displayed in the legend.It Specifies how each legend item should be represented. Please refer below code snippet.
[C#]
this.ChartWebControl1.Legend.RepresentationType = ChartLegendRepresentationType.StraightLine;
For more information about customizing legend item image, Please refer our online documentation link given below.
http://help.syncfusion.com/Ug_101/User%20interface/Windows%20Forms/Chart/Documents/customizinglegenditemimage1.htmFor your convenience, we have modified the sample and the same can be downloaded from the following link.
http://www.syncfusion.com/downloads/Support/DirectTrac/General/F102913-15136714561486720867.zipPlease let me know if you have any other questions or concerns.
Regards,
Siva