Terrain brush details without the terrain?

Hey I have a scene with a modeled ground plane. It is largely flat, and I have setup a terrain system just underneath it, because I want the terrain grass brush detailing. It all looks OK, but the terrain is static so that the brushes accept shadowing as they need to, The terrain then contributes to the beast light maps.

Is there a way to have JUST the grass billboards? I never need to render the terrain or have it cast/receive shadows

 

You would need to make your own system. Grass is completely tied into the terrain system.

 

Thanks Owen, I have compromised on the lightmap size for the terrain, should be OK.