I already changed the template, that was also the only way I could find.
Our use case is a bit off scope, the PanelTabItem constains several constrols inside it, RadGridView with the results, and a few other controls...
This PanelTabItem is inside another control that controls the events of showing/hiding the PanelTab that contains that PanelTabItem.
In the PanelTabItem header I set the refresh button the close button, etc...
In some occasions, the user wants for this particular PanelTabItem to appear without anything around it, just the controls that are inside it.
Sounds crazy??? Yes, a bit, but that's what he wants :)
I might move everything that's inside the PanelTabItem and create a new separate control and show that inside a popup or something. But for now, I will use the style and set it accordingly to the user requests.