I have seen various installations online of people upgrading their radios with products such as the Seicane Android head units (which primarily catches my interest.) My only problem is that I already have the factory navigation unit in my car. I'm wondering if there are solutions for retrofitting a unit on top of where the screen is now or replacing it. I don't want to install a unit below and keep the old navigation screen, though. Does anybody have information or experience with this?