Geoffrey Trott, General Manager of Airhead, has been kind enough to respond to my inquiry about this topic. I get the impression it is "not cool" to directly quote such a response here, so I will paraphrase: The issue exists to some extent on paper, but does not seem to exist in practice. If an individual wants to comply with the letter of the law, the Airhead can be modified as follows:
1. Install a pumpout fitting to the head (and not use it)
2. Replace the thumbscrews with 1/4- 20 machine screws to "permenantly mount it"