Now we have confirmation of the required track spacing from the O gauge section, the running track design has been slightly updated.
One change is moving the N gauge track to the inside of the boards; this provides passive provision for a seventh track to be installed between the N and EM tracks. This picture shows the location of each track together with a representative train size:
Depending on the gauge of the seventh track, it may or may not be possible to run trains on this track together with trains on the N or EM track.
This is the updated top view, which has now also been drawn more accurately:
This is the updated possible construction method for each board:
The overall size of the running track (including the extended running track option) is unchanged; see the Replacement Running Track post for more details.