Anyone have experience bringing their dog on board? (Paid, not service dog.)

We have 15 lb poodle we may bring on a Frontier flight. Frontier rules state the pet carrier cannot be more than 8 inches tall. Our Poodle is 11 inches tall. Obviously if he lies down he'll fit fine and we can "squish" the container some if the limit is really 8 inches on Frontier.

Just curious if anyone has a thought or experience with this same situation. Thank you.