I can't find a guide to it. Only that it can be done by belt, thumb or towel and that it can be dangerous like everything in this world. But nothing about it's effect. I don't want overbite.
I have a bit of monkey face, a roman bump on my nose and consequently a mid face that is dropped. Maybe it is because I can't produce as much force with the middle of my tongue as with it's front or back or root, it gets numb in the first 3 secs and even if I would tongue chew or practice: my palate is too steep there for my inflexible tongue to fit on it. Something like this:
The arrow is where I should push? D:
What is the shape of your palate?
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I think thumb pulling is nice because you can apply more force than the tongue, loosening the sutures and then maintaining the changes with normal tongue mewing. In your picture, Is the arrow pointing closer to your teeth or to the back of the palate?
unless you're 'facepulling' more hours than you're not, don't bother. Any changes you make (and that's a dubious claim) will just move back overnight or when you're not 'pulling'. Sorry, but correct growth is a one time deal. You need to wear plates (I did) or perhaps mew obsessively if you think you're still growing (I'm not saying this will work, only that it hasn't been outright disproven).
https://reversedental.wordpress.com/photos-year-3/