Thanks for the replies, gents, but there's not going to be any other software packages that I have to learn, especially since I needed this item by the 14th. Probably won't get it in time, but we'll see.
I drew originally in sketchup, and used a plugin to export in STL, and then rechecked the file in Lamina. Everything came out okay in Lamina, which showed what wasn't connected, what needed adjustment, etc. The original was drawn in MM, in Sketchup, and converted to inches in Lamina. That conversion was dead-on balls accurate.
"Up" in one program might be "width" in another, but the dimensions are the dimensions regardless of the axis There is no good reason for any one program to resize what another does. None.
At any rate, I redrew it from scratch in Sketchup, in inches and millimeters (two different files, two different drawings) and then checked both in Lamina, where they came out identical in both respects. Uploaded the file that was in inches, and suddenly, it was 19" in length, with a price of over $110
So, I redrew it again from scratch in mm, in sketchup, (simplifying one or two of the details by finding an easier way to draw it from practice) and now it shows exactly what I drew in the exact scale I needed, after the upload here.
That tells me that it's Shapeways, and not me, since this is the only place that's resized anything.
I hope this time they don't find anything wrong with it, (especially the raised letter, because that's just a silly issue) because I don't want to have to do this all over again somewhere else.