For some reason I couldn't find a reply button for the Proxy thread, so i've made this new one.
Railclone objects are essentially made up of two things:
1) Sweep profiles (ie. road)
2) Cloned elements (ie. lamp-posts)
Most of the time, the cloned elements add the most to the polygon count, and the thing is, they don't need to be deformed. I recently had to create an elevated monorail track that serviced a ~20x30km area, and it's bloody huge! What I did was to choose and non-deformed objects and do the following:
1) Copy the segment, replace the cloned elements (columns, etc.) with long triangles at their origins, and delete the deformed sweep (the track).
2) Copy the RC object, rename to "Spawner_RailClone_Something", and replace it's segment with the new one.
3) Use this new RC object as a reference object for Forest Pro to place an instance of the columns at each triangle.
This made viewport responsiveness a lot better, and gave all the other advantages of FP like instancing (lower memory), frustum culling, etc.