Im a visual person too! And sometimes cockerals would shed or thinning out their neck feathers, making it appear very LONG back. Someone mentioned you need a bit of slope on the back instead of STRAIGHT like RIR.
I thought Happy Chooks' Moose had a good example of a back length, not so long, not too short but moderately long. And a good depth of girth/chest.
If you question about a bird's width and depth, would hand feeling the bone structure and muscles would verify how "wide" or "how short". A bird can hide some conformational defects with fluff. Keel bone is another one, the bird might look fine but upon feeling it, it was twisted or deformed...surely not the kind you want to pass it down.
Pay attention to the legs and gaits. I've been seeing some "knocked kneed" or cowhocked birds a time or two, more predominately in Leghorns and "lightweight" breeds.