... However, when I interrogate the Space units in Model space it shows "Architectural" and "1.000000 : 55.367181".
In Modelspace, that Space_Units/Scale/Model_Space setting just controls the printing scale. It's a common misconception that it affects how the Objects within Modelspace are represented/drawn/shown. I wish they would change the heading on that Options section to "Printing Scale", or something.
Paperspaces behave differently-- perhaps more like what you are thinking how Modelspace behaves.
It is commonly accepted best practice to not print from Modelspace. To print (to PDF, or actual paper), it is commonly accepted best practice to:
1) Create Named View(s) in Modelspace;
2) Insert those Named Views into Paperspace(s) via Inserting Viewports;
3) Set the desired printing scale of the Viewports (and thereby, the printing scale of the views of the Objects within the Viewports) in the Viewport Properties (selecting the "Fixed" option, if desired);
4) In Paperspaces, keep the Options/Space_Units/Scale/Paper_Space setting set to Full-Size
So my hoped for 1" = 1' in Model space is shot.
It's easier and simpler to work in Modelspace drawing full-scale. Otherwise, all the math has to be done and kept track of by the User. Because, as I said, in TurboCAD Modelspace, that [Printing] "Scale" setting in the Space Units options doesn't affect the size of what is drawn or how it's reported in the Inspector Bar or in the Metrics in the Selection Info Palette.
If you are working with an other-created
drawing that perhaps was done the old-fashioned
way (drawing in Modelspace a different scale than the real-world size, so that when printed it fits on paper as desired), I would go into the Space Units option and make whatever changes I needed there to get the Modelspace Objects to report
the same size as in the real-world. One suggested way of achieving this I mentioned in my previous Post.