Hi,
You can use the SegmentYCounter attribute to calculate the Z Fixed Translation of used Segments and the Sequence Operator in the Increment at Y mode to alternate rows (by the X Fixed Translation). This RC object can be used as a base surface for the FP object, which can be easily limited to desired Surf.Mat.ID.
Attaching a sample scene with simplified possible scene set-up. Hope you'll find it useful.
Best regards,