How to add a group to multiple built-in Ribbon tabs (vsto)?

For anyone else pulling their hair about this, the only way I was able to see my group on both Appointment and New Mail Message tabs was by adding one Ribbon for each built-in tab, and then copy/pasting all of the UI and code from one Ribbon to the other. Make sure you choose proper RibbonType (a property of your Ribbon) for each built-in tab.

The designated answer is now obsolete!

1. On the OfficeRibbon object, set the RibbonType for as many cases as necessary (e.g. Microsoft.Outlook.Explorer and Microsoft.Outlook.Mail.Read).
2. Add a first Tab and set the ControlId.OfficeId (e.g. TabMail)
3. Add another Tab and set the ControlId.OfficeId (e.g. TabReadMessage)
4. In each Tab add a Group and a Button within and set the Button.Click event to point to the same OnClick method