Has anyone used the companion cert to secure an extra seat for relatively low cost?

Between my wife and myself, we have three annual companion certs. I am debating whether to close my AS Business card (which would leave us with two certs from our personal cards) since we sometimes don’t have enough expensive “companion travel” to make great use of three certs. This year we gave one cert to family because we weren’t going to use it.

I just looked, for other reasons, at the AS policy page for PoS (passengers of size). Turns out you can be your own companion!



So if I had a spare cert, I could secure myself a guaranteed empty middle seat for $99 plus taxes/fees? (and the annual card fee, of course) and perhaps even get the cert back if the flight isn’t sold out? And earn redeemable miles for that seat?

Would I be able to use the companion pass for a round trip with my empty seat? How would the return of the companion fare code work if only one leg was less than 100% full?