Tracking a SOP/GEO to optical flow edges

Hi there, I was hoping to get some outside ideas on this project I’m working on. I’ve created this lovely little worm geo from SOPs, and I’m hoping to track it to the edges of people using optical flow. Visually, I would like it to look as if they’re nibbling at the edges of the optical flow like one of those live fish feet spas? So when you walk into the frame you’re surrounded by these little guys. I’ve included a screenshot of the important part of my project. I just can’t seem to think of a way to track the geo/SOPs to track to the edge of the optical flow. They should be instanced to the edge some way so there are multiples of them, and so they follow it, but I just can’t figure out how to and can’t seem to find a tutorial even close to it online. Let me know if you even have a brief thought.