He writes about it on his blog and mentions the fact that the first version of the model was unfortunately too small. Fortunately the next version was just the right size, and the process of building the model can be found here and here.
I made a comment wondering what it would look like for Nn3, and he generously sent it along.
Comparing it to the pictures that Russ has on his site you can see that it is quite a bit oversize for Nn3, but doesn't look too far out of scale for standard N scale.
I guess I'll just have to build it and see how it looks.
