Thank you so much for taking the time to look around. I've found nothing that supports arching the tongue to change the pitch either but as the old saying goes: "10,000 frenchmen can't be all wrong". There's a bunch of people out there that advocate this method (I use it too) but as to "why", this is a mystery. Well maybe a little less a mystery if what's been uncovered about the link with the jaw and vowel sounds cuts the mustard. I hope that someone grabs this idea and goes with it in an academic sense. Even discovering that it isn't what is thought is cool.
I'll keep plugging along and if I do find something that supports (or doesn't) I'll let you know.