As the primary route of the mainlines is established and the descending grade in place, the ground surfaces can now be roughed out with foam.
In this view, the dual mainline drops 15 feet at a 1% grade over the course of two-tenths of a mile. Also seen is the logging branch rising up at closer to a 3% grade, thus reaching an elevation much closer to 75 feet over the same nominal distance. The furniture company will sit in the elevated space seen in the distance. Foam has been glued in place as filler ... I prefer foam over the concept of screen and plastered paper as I want a firm base that will better accept and hold planted trees. Also, the foam can be added in such a way as to build up areas and be carved / shaped after roughing in the terrain.
With a bit more foam still to be added to at least cover up to the curves panels between the sections of the module, the general shape is developing. At some point, I'll come back with a hot-wire cutting tool to carve the foam to match up with these curves to form a smooth transition between sections.
As I go, I consider how the terrain can accommodate various individual scenes. In the first pic above, you could see the space that will eventually be the home for the furniture company that will be connected via a turnout from the logging branch line. Another scenic area along the branch presents itself in this view along the inside of this left hand curve. I could have easily just filled that area in with more hilly terrain but I'm thinking for now that this area has potential as something more, just not sure yet what that might be :o). Also, still thinking a bit on how the terrain will be shaped along the sharp drop-off of the logging branch line through this curve. Below it to the right is another scene area to be considered.