Managed to get the node walls measured and cut out. For simplicity I've made them a basic 10cm cube. As can be seen in the picture they look pretty tall next to the 28mm figure, but this is down to the tunnel tubes. They are high enough to take a 28mm mini on a walkway (for figure stability) and have a diameter of nearly 60mm, so the nodes need to be quite large. A base wasn't cut out to give more internal height as I plan, at the moment, to take advantage of the height and put a short walkway inside. I'll have them on a larger base to give me othe option of external pipes anyway.
For the outside finish I thought I'd try cutting out some of the foam, so that the wall ends are covered. Still a bit rough, but works well. I haven't decided on a finish for them yet. I may be just paint or it could be a thin layer of wall filler ("spackle" I believe to our US cousins). I removed the foam again on the roof to make a neat lid. This will prevent it falling off during a game. The lips of the lid will be strengthened by a top layer of something ("design" dependant). I've made 3 nodes. One will be a link node, so will have to have holes for 2 pipes cut in the walls. The wall holes still nedd to be done before I can glue the walls together.
Next week I hope to get the tubes cut to length, the wall holes made for them and maybe even cut the pipes length ways to allow for access.