That doesn’t work from my understanding, because there is no “spline mesh” to project down onto. That’s the core issue, there’s no way to currently get the “spline mesh” at all.
All you’re projecting down onto is the spline (not the spline mesh), because that’s the only data Epic gives you. Perhaps I seriously misunderstand something, but afaik, there’s just no way to get the actual spline mesh or its points. Which is why I’m stuck 
I do appreciate the thoughts and suggestion however, lmk if you have a better understanding than I do!