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In order to effectively handle this situation, we should have a mechanism which rotates the values of the Padding set to the tab items, in relation to the the text alignment, the tabs alignment and the close buttons. Such a mechanism does not exist at the moment, however. What we can do to improve the behavior is to set the TextAlignment of the tabs to MIddleLeft. This will result in the look shown in the attached screenshot. You can additionally improve the behavior by setting a Padding value appropriate in this specific case. Such a value would be (6, 4, 2, 2). The result of this action is shown in the second screenshot. I am attaching a modified versions of the themes that have the described properties set.
I have updated your Telerik points for the feedback. Let me know if you have additional questions.
the Telerik team