Great little "big puzzle" brit...
Could it be adapted to a smaller scale one person "toy"? Any chance of the SKP file? Whether I use it or not it could give ideas for other projects... though bear in mind, I could possibly share it.
Talking about SketchUp,
It took quite a lot of experimenting with McDonalds coffee stirrers and sewing pins before I got the linkage lengths and pivot positions worked out correctly.
Did you consider or actually use SketchUp to plan the outlay?
I often use arcs of travel/intersection to plan outlay... sorry been looking for a good example, but after about 30 mins of searching I gave up... guess I may have deleted them... normally I would store them all in a $guidelines layer, but couldn't find any
If your first cut is too short... Take the second cut from the longer end... LBD