Norton, welcome to the NSDA Bulletin Board.I consulted a hypnotist about 20 years ago when my SD was undiagnosed - at this time I was under the mistaken belief that my voice symptoms ought to be under my control somehow. There was no benefit whatsoever.
Although several of us on the BB have tried a variety of 'alternative' treatments for SD, there is no history or pattern of any one method permanently helping a significant number of genuine SD patients.
SD is the voice that results from laryngeal dystonia - a neurological movement disorder. Given the neurological etiology of SD, I would suggest that hypnosis is as likely to be successful as it would be for other neurological disorders - eg Parkinsons, MS, etc - in other words, not at all.
Good luck, and let us know how you get on if you decide to try it.
David Barton (AD/SD, Auckland, New Zealand)