Locked myself in the office this evening and made good progress on the lever pull-the-tab page. The movement is silky smooth. Pull the tab and the see-saw rocks.
The force and load arrows stay vertical and the mechanism itself is quite neat.
I showed it to #1 son who was suitably appreciative of the front of the page. When I flipped it over and showed him the back where the mechanism is displayed in all its glory I got the full "Woah! Cool!" reaction.
He is his father's son.