High hits or misses out of tree stands are as much a result of visual misperception as shooting technique. The critter looks smaller from above so we tend to overjudge distance. Also, the eye tends to be attracted to center of the animal's body, up/down. From the ground, center body will take out the lungs. From above, it's a pretty high shot, and if one shoots just a little high on top of that, it becomes a bad shot real fast.
The higher in the tree, the more acute the shot angle and the smaller the target for a killing shot becomes. These are the reasons I don't like to get my feet more than 12-14 feet off the ground.