Use planes rather than simple box collision?

Whenever I want to use simplified collision meshes for more complex meshes, I always have to import a closed-off 3d mesh (hull). Turning off simple box collision, allows the engine to use the default mesh polys as collision (which could be a plane rather than box).

Is there a way to use planes as collision rather than 3d hulls (as a separate mesh from the default mesh)?

The reason I ask is i’d like to add subdivision to meshes for rivers (so I can use world-position-offset to add movement to the water surface), but still use a non-subdivided version of the mesh for the collision (without needing to convert it into a closed-off 3d hull).

Actually. I guess there’s nothing stopping me just extending StaticMeshActor and have two separate meshes for the visible mesh and collision mesh.