Hello Oleg ,
By design the DockHandle is not persisted in the DockState.
Unfortunately we found, that there is a bug with RadDock when you set the DockHandle dynamically. Due to this bug the RadDock is with a titlebar after the postback. We will do our best to fix it for the official release of the control. Your points have also been updated for this bug report.
For the time being until we fix this issue, you can set rdo.DockHandle = DockHandle.None; on each postback.
I hope that this will help you. If you have any other questions please let us know.
the Telerik team