S-curves cause derailments, especially when backing. The fix is simple - have one car length of straight track between any curves that twist in opposite directions. Any of the layout design books explain more fully the hazards of S-curves and how to avoid them. I decided to eliminate a runaround track, as there wasn't space to park fifteen cars and a caboose on it. The loop itself will just have to suffice as a runaround.
Some compromises have to be made on such a small layout.
A triple switchback is in the yard, again not very realistic, but adding to the fun of operating, and giving some extra sidings. Here is a view of the track plan. This is made in two sections. The lower eighteen inches detaches for transporting and is 2 X 4 feet. The top eighteen inches is 1 X 4 feet under the yard only.