You could get an instance of the main RadAjaxManager using its GetCurrent() method in the content page server side and add programmatic ajax settings for the needed controls. Also you could add a asp Timer control in order to trigger the UserControls loading. When the timer elapses, you could load the user control you want and show LoadingPanel which could be set as DefaultLoadingPanelID for the main RadAjaxManager.
I hope this helps.
the Telerik team
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