Steve,
a 30 degree angle and 300 yards. So, in order to hit the target one should aim the gun as if the animal were only 261 yards away not 300 yards….. and for the 70 yard shot with 60 degree downslope to hit the target one should aim the gun as if the animal were only 35 yards
http://www.wildsheep.org/magazines/article_uphill_shooting.htm

Cheers
Johan