Step one: lay your chosen track.
Step two: highlight the track with the select tool.
Step three: click the offset tool, and set its spacing to 0.51 (you will need to adapt for other foreign narrow gauge rolling stock if used.)
Step four : go to miscellaneous in the track section, and click (CC SG 3rd Rail Static 2)
Step five: click the 2 yellow offset boxes (you will have to reselect CC SG 3rd Rail Static 2 after clicking the first box).
End: you now have a working dual gauge track system. please note that you will have unrealistic junctions.
Thank you for reading.