Hi,
The Auto align option within the Extend X/Y Size to Area mode should help you with this task. This option creates an array aligned automatically with each sub-spline. This feature is very suitable for roofs and panels. Two modes are available. For both modes, the Z axis is always perpendicular to the plane formed by the spline. a) "X --> XY": The X axis is parallel to the RailClone XY plane (considering the local axis of the object). b) "to Spline": The X axis is aligned with the first Spline segment (you can use the "Make first" vertex and "Reverse" spline operations to modify alignment).
To align (overlap) these panels - Segments as needed, using negative Padding (Left & Right) values should do the job.
I hope that helps.
Best regards,