If you want a hum cancelling split coil pair when in the middle position then you need the bridge slug, neck screw combo like in
this diagram. It's a little more work to wire, but probably worth it in the long run. Just make sure you have the slug on the bridge, as it's furthest from the saddles.
The specific coil layouts can vary between manufacturer so I find it's useful to connect the pup coils together (using clip leads) in different combo's direct to a headphone amp in a nice EMF rich environment, like lots of fluoro lights. You soon hear the difference when you have a north/south pair.