Now what kind of spine shot are we talking about? The one that is out there 20+ yds or the one that the animal is with in ft of your tree? If it is a straight down shot I am taking it every time! I have succesfully done this more than once. As far as it beeing unhumane, how? There is many vanes and arteries around the spine no different than the above listed heart shots is there? As far as little room for error, I dont see it either. Now shooting straight down 20 ft in the air I am going to put my arrow through the spade on the Ace of spades playing card EVERY time without fail. How big is your double lung shot on a quartering away shot at 40 yds? I guess about a 4" target. Hmmm....a 4" at 40 yd or a 2.5"X3.5" at 0 yds. I will take it without a doubt!