The thinking was to find the faces which had an edge touching the outer perimeter. This could be done by checking the distance between the midpoint of a face edge and the outermost perimeter. If the distance for one of the edge midpoints is 0, then the face is touching.

- So first was to join all the faces, get all the naked edges, join them, sort by length and get the longest curve (the outermost perimeter).
- Next, taking the naked edges off all the faces and evaluating curve at gives 0.5 gives the mid point.
- The Curve Closest Point component gives the distance of these points to the perimeter.
- The smallest of all of these values are checked to see if any equal 0 using the Equals component, which gives a True or False output which can then be used to Cull the faces.