@coaster, @lensman: Thanks for the compliments.
No offense to any metric folks, but I grew up on the Imperial system, but I'm also an engineer. When I design things, I use real world (1:1) dimensions in decimal feet. This building is 16 feet square, so the length of a side, whether I'm using Truespace, OpenSCAD, or Blender, is 16 units.
That way, I can take my trusty tape measure and go validate that some object is the correct size.
As a final post-processing step before uploading to Shapeways, (for 1:220 models) I multiply "feet" by 1.385 to get "millimeters". It's just that simple.
To handle the wall thickness requirements, then when I'm designing for FUD, I make sure that everything is at least 3" (0.25 feet) thick. For FCS, it has to be 1.5 feet thick. As I'm drawing, I don't think of it in terms of units the printer needs, I just keep that 0.25 foot limit in mind.
I will grant you that those who use the metric system have it a bit easier.. they just measure in millimeters and then divide by their scale. I'm perhaps a bit too old of a dawg to learn that trick.
What is rather interesting about doing miniatures is that humans tend to perceive the size of buildings based on being on inside of them, rather than the outside size of the structure. We tend to lose sight of the 'real size' of a building quickly. I grew up camping in a one-room log cabin that was 12x20 feet. Today, that cabin would actually fit inside my living room. But, if you take the two models and compare their exteriors, your brain says "one of those is not in the proper scale". But.. I can prove that both models are the proper scale.. I've got my trusty tape measure. <grin>