Items to automatically adjust position when PanelBar has no scrollbar. See attached project.

DECLINED: AdjustPositionOfPanelBarItemsNoScrollBar SDK sample demonstrates an approach to customizing the RadPanelBarItems to include a ScrollBar when the RadPanelBar's vertical ScrollBar is Disabled.
https://github.com/telerik/xaml-sdk/tree/master/PanelBar/AdjustPositionOfPanelBarItemsNoScrollBar