Thank you for the question.
Currently, in order to set the preferable properties for the header, you should first set them initially in the Form_Load. Since these properties will be reset when you change the group selection, you should set them again a moment after the PanelBarGroupSelected event handler ends.
We will consider making the header customization easier in one of our next versions. I am attaching a sample project to demonstrate the current approach.
I hope this helps. If you have additional questions, feel free to contact me.
the Telerik team
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