Adjusting clone spacing along a spline

Hi

I want to create a necklace of spherical beads along a spline with smaller beads at the ends but I need the smaller beads to be closer together so that the space between the edges of the beads is the same (spacing of clones is proportional to their size). I’ve used a plain effector with falloff along the spline to get the scale but I can’t see how to get the spacing.

Thanks
Chris