Power Mesh that goes off screen?

I am wondering if there would be a technique to use PowerMesh to apply a sign to the side of a millipede that walks in to the shot from, the right. Obviously the area of its body to add the mesh to would only slowly emerge from the right, so would this make it impossible to use PowerMesh? Presumably the full area would need to be visible at all times?

In these situations, it’s best to start when the insect is fully in view and generate your mesh from there. You can then track backward and forward from that point in time. You don’t need to only track forwards.
When the mesh goes offscreen it stops trying to track the mesh points that aren’t visible and just follows the planar movement.

Depending on the shininess and size of the millipede in your shot, you might want to only utilize translation when you track the planar part of the track.