When shooting at extreme angles whether it be uphill or downhill the arrow flight will be less than the yardage your rangefinder reads. Rule of thumb is to reduce the yardage by 10% when shooting at a 20degree angle. 20% at a 30 degree angle, and 33% at a 45 degree angle. 45 degrees is very steep. So if You are on a cliff that is 50 feet above the level of the elk and your range finder reads 40 yards you would need to shoot it as approx. 35 yards. If you are a 100 feet below the level of the elk you would need to shoot it as 27 yards. Or do as I do and get within 30 yards and I use the same pin anyway.