Creating a mesh form-work for a cave

Hello,

I have a 3D scanned data of a cave that needs to be replicated using CNC for the mold and FRP form-work. The cave is rather large (30m x 10m x 10m [w x l x h]) and will need a solid structural system to support it from the back. 

ELEVATION
PLAN 

What I need to do is create a mesh network that is composed of straight segmented pieces. To start, I contoured the surface at 500mm segments in the X and Y axis, getting a mesh grid [below]

Then, I wrote a simple grasshopper script to segment the contour lines, but when I run it, the segments in the X direction and the Y direction do not intersect like I need them to. 

I understand why this happened and I understand what I need to do (in concept) but I can't seem to figure out how to implement it. 

I'm pretty sure that I need to take the original contours and find the intersecting points and include it in my set of points from DivLength command. My problem is that in the list, the numbers get all jostled up and when I Pline the list of points, it goes a bit crazy. 

My questions are:

1. Is this the best method of going about this process of creating the segmented mesh?

2. How do I reassemble the list of the two point groups I added? 

Thanks in advance!

Best,

Issac