I am not quite sure what is your exact setup and I prepared a simple demo project based on my assumptions.
The project contains a RadDock, which has a User Control in it. When you move the mouse over the User Control, a tooltip which is larger than the RadDock shows. Part of this tooltip is inside the dock, and part of it - outside.
In case I have not understand you correctly, please open a new support ticket and send me a sample, fully working demo
along with a detailed explanation of the desired behavior and some screenshots. Once I receive it, I will modify it in order to meet your requirements.
the Telerik team