Hi Jacob,
Thank you for contacting Syncfusion support.
In our current implementation, we have maintained the height of BackStage based on the height of the form in which it has been placed by comparing the MS Outlook. Can you share whether you would like to show the BackStage as popup when it is opened and make the RibbonControlAdv visible in the backside? If not, can you share more about information about your requirement? Based on your update, we will proceed further on this.
Regards,
Keerthana J