Contours from Imported polygons

Working on gaining control of my grading. In generating a model of contours for model homes, I am using contour survey generated in datacad. I create the contour lines using the horizontal polygon, changing the z setting to control elevation. When imported into sketchup, horizontal polygons stacked and set back as you rise on the slope. I use draw-sandbox-from contours and layout the grid that adapts to the height of the polygons. That is pretty good. However, I seem to be getting edges of the polygons in the finished image that includes the triangulation the program generates. Mostly it is below view. However, I am not able to set the original polygon’s active to delete. To explore this, I took a screen save with one section of program generated triangles deleted to make what is below visible. I can not get the select tool to highlight the polygons under. You can see the affect of overlaps in picture.

Tips always appreciated. Thank you.

(Have you tried Fredos TopoShaper plugin for this?)

You should delete the helping structure under the terrain.

No, what is that?

More infos about the plugin here: [Plugin][$] TopoShaper - v2.6a - 24 Apr 21 • sketchUcation • 1

I was concerned about deleting the construction polygons in case I needed to make a change. However I discovered I could move it at a fixed dimension and put on a layer that would not be displayed.