The answer to your question is to shoot the shot as if you were on the ground(as far as yardage goes).When using a rangefinder from a tree,try to find a tree beside the animal,if possible,and range it at eye level instead of the animal.This will get you much closer to the actuall yardage that the animal should be shot for.Optilogic sell a rangefinder that will automatically adjust for this if this isn' t something you will be able to do.



Another problem is how high you are.This creates an extreme angle and makes it harder to catch both lungs due to the angle.You may have actually shot over the first lung and only caught the second.That much height allows very little room for error.