Cuts that narrow are really hard to do Esko. I've tried a few times but my failure rate exceeds my success rate. Use a new cutting wheel for starters. I've tried putting the pane on something like a ruler with the score line just over the edge and placing a board on the piece to be broken off and tapping it with a hammer. That improved my success rate but is still not perfect. Although that method works very well for cutting floor tiles. Maybe someone has a better method.
Someone I consider a master woodworker once told me that a master woodworker is not someone who never makes mistakes. He is someone who is able to cover them up so that no one can tell.