How to change the landscape material/layer underneath a pair of parallel runtime spline components?

I am building a ski resort builder, and a main part of this is building pistes. As part of this I make a main central spline, then get these points, offset the location and make a new spline either side, parallel to the central spline. I then line trace through the terrain to add points, to make sure that the piste doesnt go through the ground, then finally place piste poles at every few spline points. I would now like to change the landscape texture between the piste, to make it look more worn and skied on. Ive tried rvt’s and procedural meshes but apparently they arent compatible. Could someone please explan the best method for this?