I followed uc4me's lead with the tailgate net. It's been successful at keeping my 80 lb lab in the cargo area. Has also done a good job at keeping cargo from rolling forward when geared up for longer trips.
I have seen some elastic net products (with a pocket) advertised a bunch that connects to the headrest assembly and then to the meet base. Considering giving one of those a shot for the added convenience of being able to store things there like water bottles, docs, etc.