I am really jealous. The point you are at is my absolute favorite phase of layout-building. Once you start plastering, the whole layout magically transforms from work-area to terrain. I also love the scale you are working at.
I hope you don't mind if I kibitz just a little:
In this part of the scene
I don't think you are going to like the final result. I think it will look like the jutting arm of the terrain was built to justify the portal rather than the reverse. No real tunnel would be built that way. If it were me, I would build out the steep contour in the foreground a bit and turn it into a cut right up against the foreground track. Just my $.02
