The use of these seats would preclude access to the rear of a coupe, which may not be a problem, but if this is a road car, & it is rear-ended, & the ADR [Australian Design Rules] say that your car should have head rests, then your insurer may well wipe you like a dirty ar$e. You may also find yourself paying the medical bills too.

Whiplash injuries [that headrests were designed to minimise] can cost a bundle.

Caveat emptor [Buyer beware]