modeling a loose pin in a guiding groove track with loose play - similar to "point on curve" , but with play between pin and grove

we are moddeling a barrel cam shift system similar to sequencial transmission. The path of the guide track (groove) is perpresented by a spline, then we have a "point on curve" bloc to have teh shiftfork pin follow the track. very similar to the example: using-the-point-on-curve-block-flapping-wing-mechanism.html

however we want to represent that the pin is smaller then the track groove, aka it has some play or loosnes to it.

point on surface only works with flat infinite 2d plane, not on a 3d curved surface.

any suggestions welcome.