Hi Andrei, re: script version without UI - unfortunately I think it would be difficult for a script to work only by a slight modification of the existing command, because I don't think the script will have a reliable way to figure out which particular face in the generated object should be deleted.

So a script version would probably have to work fairly differently from the regular command and instead build the pieces like side walls and top piece itself and join them together. That's not a small change to the existing script, it's a pretty different thing and would be somewhat time consuming to develop, so I'm sorry I probably won't be able to make that right now.

But why wouldn't the other method that I was describing previously work for you? That would be where the base surface would be deleted when extruding a face that's part of a joined surface, the extrusion would basically become another part of the joined surface structure.

- Michael