Quote: "3x3 tiles is maximum of what You can do when You make Your Own Segments/Entities"
Youv'e been gone longer than I thought, since long time ago and the introduction of null space segments MUST be 1x1 for enemy collision, never was a size limit (except over the grid size) for entities (but only for player collision, entity's never did have enemy floor collision). If your willing to put in the time and effort any mesh can be sliced up for enemy collision.
I wouldnt feel awkward about missing that info though, even most users who have stuck around seem to have missed it.
However having said that 3x3 will still work provided the mesh sits above floor level and you can place stock segments beneath it but enemy characters can still get hung up on the centre segment of te custom mesh.