Dave, I must say I really like the most recent of your designs. Especially if there is a way to work in a passing siding. Mark, from my experience, the diesels will perform significantly better on the grades than the steam engines will. I run a 4% grade on my layout. Overall, I don't have too many problems any more, but steam engines really struggle with any imperfections in the track. I learned this very quickly when troubleshooting my build. Smaller wheel bases are more forgiving.
This is really turning in to an interesting thread! I look forward to seeing how your planning and implementation progresses!
Best,
Marc