It absolutely depends on the height of the ball valve. Try to get the ball valve opening as close to the bottom of the cooler as possible to minimize wort loss. If your cooler has a depression in the center that leads to the drain (or where the drain would be as some coolers do not have a spigot installed), you might want to put the valve slightly higher, so it is easier to screw on. Bazooka Screens aren't very flexible at the threaded end.
Make Beer, Not War.