3D printing Site Tile Defintion

Hello,

   I am trying to write a definition for my office that allows us to export topo models out of revit, and automatically create site walls, join the meshes and offset them to a desired thickness.

    I think i'm about 80% there. It may not be the most elegant procedure, but it appears to be working.  I am having some slight problems.

1. I'm having trouble extracting the edge curve on one side of my mesh

          a. I used a mesh plane intersection to trim my site mesh, and the resultant curve extends beyond the limit of my mesh

          b. I identified the intersection point, but GH is not shattering on that intersection point. instead it happens at a point further down the polyline

2. I'm can't join my curves. If i bake them, they join into a closed curve.... GH join curves is not behaving. i've had some success joining two segments, but i can seem to get all 4 side wall curves to join.

if anybody could offer some advice, i'd be very appreciative. also, i'd like some recommendations for ways to streamline this definition. I'm sure that there are more creative ways to manage this data, and i'd love to about them. thanks - CSDG