I pass on this shot hoping I will get a quartering away shot as he walks away. You can always draw and let a soft grunt with your mouth if he doesnt turn far enough. He may turn to look back behind enough to give you a decent shot. I actually have killed a lot of deer with the straight down shot. Probably at least a dozen does and one mature buck. But I have also lost two really good bucks with this shot. The first was back when I still shot aluminums with muzzy heads. I smacked the spine and the buck stumbled and then ran and stopped out at sixty yards with the arrow lodged in his back, bent like a horseshoe with the fletching on one side and the broadhead sticking out the other. I saw him about three weeks later and he was struggling. I never could get another arrow or bullet in him and I don't know his fate, sepsis and coyotes most likely. The next time I had that shot I made sure to miss the spine. I ended up getting one lung. Trailed him all over Hells half acre and lost him. He ended up living as I got trail cam pics the next year, the opposite side that the arrow hit him grew a small gimped up antler. Oddly enough I had a chance to kill him that fall and let him pass. I kinda felt like I owed him a pass. He ended up getting killed by the neighbor gun season. So my two cents is to let em walk out and try to make something happen. If not then no shot is taken. Just remember those big bucks are tough, tough, tough. A shot that you have killed ten does with may not be the best choice for a big buck.