V-Ray + Grasshopper Scatter for more than one surface

[Helldoor]

Hi there!

For a landscape architecture project I'm currently working on, I need to picture a hill with different pieces of forest on it. Of course I don't want to do this manually and use therefore a very nice grasshopper file, that was shown in a Chaos Group webinar (see pic attached). In this file three different instances can be randomly populated on a certain surface! This works pretty good, but with only one surface. As a 100% Grasshopper noob I really don't know how to make it work otherwise. I tried copy-pasting the whole algorithm, but in that case only the second one would render. I tried reattaching the "Render" node from the copied alglorithm to the "Render in Project" node of the first one, but then none of them renders out. Obviously, I don't really get the whole thing. And learning Grasshopper is on my To-do list. But right now I don't really have the time to do it, so I thought I'd ask you guys for help:

1. how do I get the whole thing to work with several surfaces (the "Set Multiple Surfaces" option form the RMB drop-down menu is not the answer, as the different forest pieces have different tree densities)?
2. as I'm using the same tree for the Population process, I don't really need three "Open file" slots; when I delete two of them however, it only renders one third of the trees - does it have to do with the "Cull" node?
3. is it some how possible, by adding one or more nodes, to manage the population concentration a bit - I'd really like to have more trees in the center regions of my surface and less - around the edge areas?

Thanks in advance!
Hell

[Helldoor]

Okay, now I have a somehow straightforward solution. People with good grasshopper knowledge will probably have to facepalm, but "if it looks stupid, but it works it probably isn't that stupid", right? I copy-pasted the algorithm up to the import part five more times (as I have alltogether six surfaces to differently populate) and connected all the Importers (18 nodes) to the flattened V Geo Input of the Render Node. Now it works just right.
Of course, I'll still be vary thankful, if somebody would propose a better solution.

Greetz
Hell