I ended up doing Canvasback cargo liners +
extension barrier and the
WeatherTech cargo liner. The latter is properly designed for the 7-seater; however, it is much flimsier than the Tesla OEM floor mats and has nothing keeping it in place, which means that it loves to slide around.
Cavasback fit was not perfect for my car and they are going to be sending me updated liners that should fit better. Once that's done, I will probably have to add velcro strips to the bottom of the WeatherTech mat to keep it in place.