RE: Mistyer Darby difficulty
Rink,
I use "O" scale model RR figures. Not exactly scale when you consider Mr. Darby is 1/38th (why did they do that???) and O scale is 1/48th. From any kind of a distance its hard to tell the difference. Another option may be to purchase figures from 1/35th scale tamiya kits and make them look they way you like. Sounds like a lot more work though.
As for the superstructure kit from Harbor Models, it looks nice but it is also about $350.00 Seems to me to be quite a bit of money for some styrene. I guess its all how you look at it.
Pete