For the Stich and glue guillemot, most of the points are on the say X location. (there are execeptions for the end points of some panels, and possibly on or two more)

I ran a stait line, along the bottom of my plywood, then just used my framing square to run a line up. the plotted the Y- coordinate as required. Because you know the location of the y points, you could only put the line in the areas around each y point (using the ruler on the square)rather than a full strait line you need to erase/sand off later.

I have a 6ft strait edge for the long base line, but it could have been done with a stretched string above the plywood, and transfering the points down. Then the points could have been connected with a shorter strait edge.

Good luck

Myrl