Think the best discription I have listen to for the upright correct shooting position is level stance feet at shoulder width, closed and the classic beer gut posture with butt down back and hips slightly up. Not sure where I first heard it but shoot with an old CA junior Olympic shooter who was also formally trained with the same posture. This posture works best with a very low chin anchor. The higher anchor changes things a bit but you can still get close to this posture.
Hard to do out of a tree. Big thing for me on a platform up high is my hip angle and rotating or cocking them to maintain my same sight picture and sighting angle. Straight down was the hardest for me for a many years. I have learned to clear my hips up and back, flex knees and get way over top of bow. Then, draw the longest draw I can get it this position as it tends to shorten you way up. The point of impact I look for on deer or elk in this situation is right aft of shoulder blade humps on top of back. You either slide arrow right beside spine or you break their back. Either way its very effective shot placement.
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