Sorry to Necro this thread, but I might as well make it a bit clearer on what this entails.

This uses a p2 controller, when you spawn p2 in from importing them they will show up on the right of p1. Doing this in a corner will push p2 up and over the boundary of the map. Moving Oob is tricky, but basically if p2 is completely on the top of the map, you have to move the stock backwards, up is down, down is up etc etc.