Joining in the middle of chambers or passages IS perfectly OK, indeed it is necessary every time there is a passage intersection. You just need to ensure that each affected passage has a gap in the wall to accept the join!
The only restriction I have found is that there should not be two wide openings opposite each other in the same scrap. In this scenario the scrap is ‘broken in half’ and while you will get a nice pdf output, the kml plan will not plot properly (unless this feature has been fixed recently).
In Alistair’s example, the pair of green circles indicate a passage opening that can be joined.
The pair of brown circles show a passage opening on one side and no corresponding opening on the other.
Hence Therion found the nearest opening it could in the scraps it was instructed to join, and in this particular case was trying to join the three nearest openings together. I predict that an acceptable result would be obtained if a gap were to be opened near the brown circles.
Bruce
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