We don't know your bow speed and arrow trajectory to 20 yds. I'd say get up in a tree about the same height as you will hunting. Have a friend move the target butt at 10, 15, and 20 yds and shoot groups at each of these distances. Remember to bend at the waist to keep your upper body form at the same position as shooting on level ground. Don't figure what your bow will do, know. Go out and practice and enjoy!