Jim answered the location issue - it is on a slight curve. I played with the location of the magnets by moving them around on the drywall screw heads super gluing them in place. If one wanted a larger magnet field to spot cars over you could add additional pairs to the row. Two rows of three was a comfortable compromise. Even a single pair of magnets uncoupled the cars, but the the uncoupling "zone" was only about 1/2".
Big JIm - You need a magnet field that will pull the glad hands in opposit directions horizontally. With vertically oriented poles on these magnets you need them in separated pairs to create the side pull to open the knuckles.
