Here’s a crude example using time which you can treat like percentage:
https://i.gyazo.com/b47c3eb79a1d5626…cf24119701.mp4
The shape event runs in the Construction Script (for debugging purposes). By default spline duration is equal 1, no matter how many points it has, this can be adjusted on the spline. If I set *TimeStart *to 0.0 and *TimeEnd *to 0.1, the SMC will deform onto the first 10% of the spline. By adjusting the Offset, I can move that 10% around along the duration of the spline.
You will want to use Constant Velocity here, most likely - this will give you even distribution regardless of how closely points are packed together. Otherwise the time (and space) will become compressed where points are close; you can, of course, take advantage of that, too.
You can make it work with length in a similar fashion, I’m just used to working with spline duration.
Hope it helps.