I read through your post twice and I kept thinking that your focus was far too centered upon starting and maintaining the vibration of the vocal cords and your statement,"His therapy is basically going to be slowing the initiation of voicing and keeping the voice on throughout the utterance" makes me think that you have not fully understood his theory. The valsalva hypothesis would rather have a person focus on keeping their valsalva system relaxed so that their airways do not close while vibrating one's vocal cords. In addition with practice and a proper mindset towards speech, you begin to pay less attention to starting, maintaining or stopping their vibration, it is simply a muscular movement that you unconsciously know how to do after steady practice (just like a non stutterer). I did not understand my focus in speech was misguided until about 2 weeks into the exercises when I realized that I treated words as objects rather than just mouth, tongue and lip movements while vibrating my cords. In fact when I begin to view the words that I want to say as objects again I start to "feel" the emergence of the blocks to come and I reset my focus to just vibrating and I feel them going away. Speech is simply just muscular movements with the vibration of air going through the larynx. I, like you, believe that stuttering is a neurological deficit, however, I believe it is a deficit that is caused by a person's childhood environment, experiences and perspective towards speech rather than genetic traits and is wholly curable. How long did you try the valsalva therapy?