Keith,
what you say about Sketchup's 3D matching of photos is very true. You really have to pay close attention working in three dimensions not to go off on the wrong axis by mistake or, even easier to miss, work in the wrong plane without realizing it. Setting it so that as you draw lines they appear in the color of the axis they are parallel to is a help, but I am always making multiple checks to be sure I'm referencing the plane I want. You can't just go and measure the distance between two points on a photo and get the right answer. You have to establish reference planes and work only directly in those, or you get nonsense. Hence, for instance, the critical importance of that line I mentioned in the example I showed, the line that establishes the displacement in the orthogonal, third dimension, of the plane of the cab side relative to the parallel plane of the drivers.
Yes! I like your way of saying it; the folios call out "dimensions that are a concern to the shop forces."
As far as exactness of dimensions goes, what matters to me is just how things look to me. With cabs, for instance, the 4" too long and wide cab on my #30 isn't bothering me much, while the too-narrow cab on #13 really bugs me. For me, a very distinctive and pleasing feature of the smaller 3' gauge engines is the way the cab looks oversized to the boiler, compared with standard gauge engines. So I'll fix #13's cab width for sure, but maybe not worry about #30.
It is unfortunate that this cab stuff is buried in this thread. How about if I start a new thread called cab stuff, and just reference these posts in it?
Cheers,
John
John Greenly
Lansing, NY