The scenery on the shelf above Los Gatos has always been problematic, and I haven't wanted to rush decisions. There are hidden tracks below (for the lowest reverse loop and staging), so covering the tracks always seemed... risky. When I'd put in the Alma siding, I also added room for a future, at that point undefined, industry, so I was unsure about what scenery would be appropriate. The scenery between Los Gatos and Alma also deserves to be impressive - that stretch of track goes through the narrowest part of Los Gatos Canyon. If I was being fair to the railroad I'm modeling, I'd have track clinging to a sheer cliff face... which wouldn't fit when Los Gatos is only a few inches below the track.
When I last tried building scenery for Alma a couple years ago, I thought a crossing of Los Gatos Creek might be appropriate; I had a bit of styrofoam, so I mocked out half of the scenery, used the tail end of a bag of Sculptamold to make it solid... and stopped as I ran out of material. The scene just didn't work; the creek wouldn't be low enough to be believable as Los Gatos Creek, there was no space to expose the creek bed on the fascia in front of the scene, and the tracks descending on a 2% grade across that bridge just seemed unrealistic. The scene's been sitting there half-done ever since.
The two photos here show the progress tonight. (Sorry for the poor quality and the chair leg in the photo; I should have taken the pictures before cleaning up.) I've had the best luck building scenery with sheet styrofoam. I cut pieces roughly to fit, and glue layers together with a hot glue gun. The hot glue does melt the foam, but at least some of the glue holds the foam together, and I can usually start trimming the layers within minutes of gluing, avoiding the need to wait a day as I used to when using contact cement. I then start trimming the hills with the hot wire cutter to get the rounded look of California hills, correctly angled cuts, and the like. The result are hillsides that look very California-appropriate. As soon as the hot glue is cooled and the styrofoam armature is in place, I use a thin layer of Sculptamold as the final shape of the scenery. Once the Sculptamold dries, the scenery is rigid enough for further layers of spackle or Sculptamold, and is ready for the paint and dirt that will make the hills look like... well, hills.
This scene really draws attention to the branch to Moody Gulch at the expense of the mainline. The Moody Gulch spur looks correctly cut out of the hill with minor filling and depressions along the way. The main line is still looking a bit unrealistic as it drop below the Moody Gulch spur then dives into a tunnel. That tunnel wasn't on the real SP between Los Gatos and Alma, but (1) there was a tunnel in the narrow gauge South Pacific Coast days, and (2) the tunnel is a heck of a lot more realistic than some strange cut might be.
Next steps: get rid of the bare plaster hills. The hillside along here should be a mix of chaparral (typical for the south-facing slope near Moody Gulch) with occasional redwoods in the distance. I'm also starting to think about Moody Gulch structures; I've got ideas about some additional oil well details as well as a small warehouse for supplies for the drillers.