An interesting discussion.
Having a closs look at the article that started it all it seems to me
that it was built with a different criteria to the situation in Vic.
The locos were big and eight coupled to spread the weight to allow the
5 tons axle load. These railways were built for the desert with little
or no major engineering works as an exercise in the maximum effeciency
for a railway. Imagining them used on a trip to Walhalla I don't feel
it would make it around the curves used and would require major
earthworks to allow for overhang and swing on curves. On a reverse
curve?? In other words it would defeat many of the advantages of using
a narrow gauge.
The VR ran some long trains. I suspect that the rolling stock was on
the small size to allow for efficiency in engineering in hilly country
and to make it less likely to derail. In that context I guess 2'6"
would have an advantage over 2'. I suspect the train lengths were much
longer on the VR than the NE Dundus in the photos I've seen.
I checked out another line in India that ran in hilly country also 2'
6" gauge to see the sort of loco and rolling stock; were they smaller?
The Kalka Simla line [still running] seems similar to VR mountain
country. They used 2-6-2T and at one stage 2-6-2 + 2-6-2 artics as
well. The rolling stock however, seems bigger than the VR one. Could
someone with knowledge of these lines comment?