I cut out the pattern from the plan and glue it too a piece of thin stiff backer paper that comes out of the glossy print photo paper package. Not the photo paper but the stiff piece that's included in the packaging at the bottom of the stack. It's very easy to cut accurately.
Then I use this template to draw a line directly to my half side mold of 3/4" birch/maple plywood. After deducting the required amount for the bending package (about 3/16" - 1/4") I sand the mold to the pencil line and then use this one piece to make the other side of the mold with a router and piloted router bit . Now the two sides match each other. One can use these pieces to make the plexiglass template. I don't like sanding to the line on the plexiglass as it has a tendency to mess up the line. I like to use the router on the plex then it comes out cleaner without a fuzzy edge.
Hope this is helpful!