The Nissan currently offers a "Cargo Organizer" that attaches to the various hooks in the rear cargo compartment. The convertible models also have these hook mounting points, so I think it would be safe to bet that the Cargo nets and Cargo Organizers would in deed fit.
Here is a link to the various organizers Nissan Offers 370Z owners:
OEM/JDM 370Z Cargo Organizers
We stock a JDM version of the cargo net as opposed to the USDM 350Z version due to the various complaints everyone has had regarding fitment. The JDM covers more area and pull tighter across the floor. The Cargo Organizer is also collapsible so facilitate storage in the cabin when not in use.