Aye up Craig,
Set your position to shoot downhill and if you are zeroed at 27 yds in 177 you should not be bothered with hold over or under according to my golborne comprehensive maths."at 27 yds".
My trick is to use a small cardboard box with targets siliconed on put out at 25,30,35,40,45,- max` 50 yd and a smooth pebble the size of a tomato with the range painted on in the position you expect the rabbits,- now rabbits dont read very well and my pebble method is far cheaper and "quicker" than a range finder.
Go to your spot and practice the ranges and hold