move points of an arch created in between 2 tilted paralleled surfaces

Hello, I am working on a project that created a new volume from floating points (discussed in my pervious post) and have now been introduced to a new challenge. 

Every 3 point surface generated from the volume needs to have a Vault coming out of it. I was able to find a script that made a vault were only the z values change when generating the arches, and I have plugged that into my script with the GREEN volume shown in the image below. 

My issue is that the surface, off of which the vault is coming out of, tilts depending on which base surface is selected, and the top perpendicular surface has the same values of the base surface but moved at a distance, generated from the longest length from one of the three segments of the base surface. 

In between these two parallel surfaces is where the vault happens.

The issue is that the Vault legs do not connect to the vertices of base surface because I don't know how to change my script to make the XYX values of the arch stay within the two surfaces. 

AND to add to the problem of the vault, The height of the vault and subdivisions of the arches is proportional to the base surface, meaning it needs to adjust if I "select item" another surface.