10 to 12 ft is plenty if you have some cover. Also you have to have the correct wind. No way around the wind. Most important to me, personally, is the shot angle. The higher you go, the greater the difficulty of making an ethical shot. As hunters, we owe it to the animal to do our best, and that means double lung, and hopefully, the heart. Try different heights shooting at your 3D target and find out what will work. Once you know your limits, you will know in your heart when to let him walk, or when to let the arrow do its job.