Alacran, when I do panels, I create the lock panel first. Keep the borders as narrow as you dare, top and bottom, extending them out at the rear particularly, and at the front end. Cut out a piece of cereal box or card stock like Bristol (sign) board bigger than the panel, punch holes for the lock screws, remove the lock from its mortise, and lay the card overyour panel. Press down with your thumb along the edges, creating a mark on the card, along the edges of the panel. Now remove the card and the screws, and with a pencil draw in the creases you created. Cut out the panel outline with scissors or an X-Acto knife, then lay the card on the opposite side of the stock, replacing the lock screws to orientate it correctly. Now draw around the card with your pencil, transferring the lock panel to the offside. Bearing in mind that your pencil will be outside the panel, cut away all the wood outside the drawing, including the pencil line, and you have a pretty much exact off-side panel to the lock panel. Also bear in mind, that perfect symmetry is not necessarily critical. That's how I do it, anyway.