I am not quite sure what you are trying to achieve. In case you can send me a screenshot of the expected result, I will be able to provide you with a concrete answer whether it is possible or not with the RadSlidingPanes.
In the meantime, please refer to the SlidingPanes section in our online examples
for an overview of the functionality. I believe you will be able to find the answer to your question there.
the Telerik team
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