FLIP Boundary attributes - viscosity, density, etc

[PeteB]

Trying to do a simple river sim using boundary layers (similar to H16 FLIP Fluids masterclass), only made of slime rather than water. The slime has both a higher density and viscosity than water. Activating boundary layers for new flow entering and old flow exiting works, but the viscosity and density attributes on the layers both come out of the solver as 0.0, something that's confirmed by the sim itself (there's overwash at the entry and backwash at the exit). The incoming boundary layer volume sources have the correct attribute values placed on the points, same as the main source, but I can't see anywhere in the solver where they're read (diving into the solver itself shows only boundary layer surface and vel volumes).

Before I resort to trying separate source and sink volumes for what the boundary layers are supposed to be doing, does anyone know if it's possible to inject different attributes into the boundary layer particles, or is that functionality set up to be pretty much only useful in simulating water?

Appreciate any help or points you can provide.