How to make station molds from an existing canoe?

I made a much simpler version of that device back in the 1980's.The difference was that instead of displaying numbers for the points along the section,it had a small hole for a pencil to mark the progress of the line on a large sheet of paper that was attached to the upright board.The board was attached to a pair of T shaped frames that held it upright and the whole thing moved along the hull for the various sections.A fine tipped pointer may have introduced a tiny bit of inaccuracy,but not enough to get too bothered about.