I’m assuming that by surface-projected you mean the user defined (docs and code don’t match). For user defined, if you add it to the layer and are not seeing it work, then I suspect it is the following: open your static mesh, and make sure “Allow CPUAccess” is enabled.
I’m really disappointed with this method though. It really does behave as “surface projected”, and not as “user defined” which is what I wanted. The passthrough seen through my “surface projected” geometry is not as stable as reconstructed, and induces nausea.