Hi Greg,
Unfortunately I think this would be difficult to achieve in RailClone as RailClone works be deforming existing geometry Segments. The only way I think it could be done is by using 3 pieces of geometry, the low seat, the full height seat, and a ramped transition. This 3 pieces could be modelled straight and then deformed along the path using RailClone.
I hope that helps.
Many thanks,
Paul