I don't think you can be too close, unless your in a tree stand, then "angle" has more to do with it. Once early on in my hunting experience, I was in a tree stand, shot a big doe right under me. It was drizzling rain, saw the deer jump off the arrow and watched it disappear out of site over a hill bout 50yds away. I didn't wait long due to the rain, got down and pull the arrow out of the ground, plenty of good blood and a small white spongy piece of lung was next to the arrow. Wow thought I had scored for sure, started over the hill where I lost sight of the deer. And saw the doe laying down, she jumped up and took off like a shot. Very disgusted I waited a half an hour and continued the tracking, about 100 more yards I saw a puddle of blood where the deer stood awhile. It was raining pretty good by now, long story short, I looked for that deer another two hours in the night and went back the next day with a buddy and looked for another 6 hours. Never found the deer, I can only think that the arrow was a little off center and went through one lung. A deer can run a long way spooked and with one lung. I will never as take that shot again an will always be as quite after the shot as before. I will also wait much longer before tracking and wait until the "angle" is better to get a double lung. Only deer I've losted and think about it years later.
DBar
Sorry for getting off the subject a bit,,,,,,