I think that Beth and I were taught the same, and
get the same result as those who are posting to the shoulder. I was just taught
as the FRONT leg that is to the inside of the arena HITS the ground in front of
the horse, I was to be "up" on my posting. So, left front foot hits ground, I am
on my left diagonal. When right front hits ground in front of horse, I am on
right diagonal. At least it worked for me in all my years of showing and english
equitation. LOL Here is a quick video with a girl talking about posting.
She explains it the way I was not taught, but result is still the same. She is
showing the "up" when front foot to center of ring HITS the ground.