See this article. Leupold uses this algorithm to calculate equivalent distance. Should be a very good approximation than a simple horizontal distance. And in my case the incline angle really is not that big. I estimate probably going down at 10-15degrees. Of course I have no way to verify this. But at least the Winchester m70 POI is almost exact where I aimed. I think no more than 3" from POA at 300yd.
What would be a good stalking strategy for the cow? Going from the other side of the r ...
If the wind is right, keep crawling. Inches a time. No sudden movements. Carry light. Check your gun. Try to get within 300 yd. If they are moving, try to intercept. Good news is that if they bed down they should stay for the entire day.