Thickening Tessellation Surfaces in Bent base surface Problem

Hi All,

Currently I have a problem with thickening a surfaces in grasshopper. 

I attached a PDF file showing the pictures. 

The parametric model is basicly built from sets of hexagon and quadrilateral by building each of the set through connecting points, and managing the points index so that they have these 2 sets together in one pattern. 

Without thickening, the surface can be applied to any surface.

However, the problem is when I try to thicken, as can be seen in the attached file (last picture), there is a tiny intersecting between vertices at the bottom part of the extrusion (the base surface is at the top --> I extrude it downward). 

This because when I extrude each surface in their own normal direction (pointing downward), the base (top) of each module is fine, but the bottom vertices intersect.  

And when I flip each surface normal pointing upward, the base of each model will be fine, but the top vertices will have the gap. 

As you all may realizes, this problem only occurs in the extrusion of bent surface. In the flat surface, no problem (no gap or intersecting edges at top or bottom) .

But I want the surfaces to be thicken in bent surface (without any gap or intersecting). 

I am thinking of several method to solve this: Maybe by offsetting all the surfaces outward, then loft the surface etc. But I do not know if Grasshopper has the tool for Lofting surface. I know it has Loft for curves, but not for Lofting 2 surfaces (bridging 2 surfaces with solid). 

Do I have to joint all modules (hexagon and quad) together first for it? So they have the common points etc.

What would be the steps?

Please give me some suggestion how I might solve this thickening surface problem (without gap).