With the current version of Railclone the elements can only be generated longitudinally. An Island is a particular case which leaves a hollow interior, for now RC can't solve it parametrically. However we found interesting to include a island case at the library but the object must be completed by hand. The solution is simple:
1. - Apply a EditPoly modifier to the object RC, and select the edges of the hole left in the island.
2. - After selecting all the edges we use the option "create edges" in the rollout editpoly-edit edges.
3. - We obtain a spline that serves as a basis for constructing a cover.
4. - Delete editpoly modifier, to avoid turn the RailClone into an editable mesh at the top of modifier stack and lost render acceleration.