Hello Eric Hill,
RadMenu placed in RadToolbar will overflow (the entire menu) like when placed in WPF Toolbar.
There will be no problems for keyboard navigation if the whole menu is placed in toolbar. But placing RadMenuItem directly in RadToolbar (or any other control) is scenario that is not supported. RadMenuItem needs to be placed in RadMenu in order to work properly.
My idea was to use RadToolbar as a Menu replacement. You can place different kind of controls in the toolbar to reassemble the menu.
Creating overflow behavior is not a trivial task and will require a lot of work to be done properly. Now you can bind the menu using ItemsSource and specify HierarchicalDataTemplate to specify individual MenuItem presentation. Using overflow will break this functionality. This is why we did not support it.
Let me know if you need more information.
the Telerik team