12-15ft. Any more and the angle is not right in MOST of my setups. The trees around here if you climbed over 20+ft, you would have one hell of a time seeing deer(early season),,, let alone shooting them cuz you'd be in the freakin canopy I think people who hunt too high shoot more deer which turn out as marginal shots, because of the angle. I'd say start lower than 16-18ft, learn how to minimize movement, and have fun. 20+ft just seems crazy to try to double lung one unless it was at 30+yds.