Hi Paul,
That link looks really interesting, I'll definitely read up more on that, it should come in very handy. As far as the displacement map, yes I've played around with this with great success, and typically I don't need more than 10000 instances when in comes to grass. But what I am using it for at the moment is rain particles and with Phantom Scatter it is quite easy to spit out well over that many points. I am attempting to create a scene with a lot of rain, so much so that a faded effect occurs as the scene progresses. While 10000 would be adequate for smaller scenes, I find I need almost triple that to create the effect.
Thanks for the link,
Chris.