Hallelujah - I got it working.
This is a great viewer, but getting detailed support on this topic has been like pulling teeth. This is a VERY confusing project for a novice coder - and not everyone wants to have to try to become an expert coder just to get one project done. Pre-purchase questions such as I asked should be met with more of a heads up that the current version of the pro is still very complex, and making use of all these great options is not for the novice or the feint of heart - and that detailed personal support is very limited.
Quality of product itself: 5 stars
Graciousness of support: 2 stars
Customization user friendliness: 1 star
Disclosure of difficulty level: 1 star
Felix & Mike, you could have saved me a lot of time and grief, and posted something very useful on one of the most viewed threads on the forum, if you had just given the instructions I'll post below. There are important details clarified here that were not at all clear to me from the documentation, even after many re-readings, and much experimentation.
For anyone who has waded through this thread, and wants a step-by-step like I did, here is a rosetta stone:
Publishing a gallery with rectangular thumbnails
1) Create a copy of your entire simpleviewer_pro folder; this will be your "working folder". (this should include the web and source folders)
2) Create a gallery (I used the PhotoShop script) Set the "output folder" location to a new folder (NOT the same location as the "working folder") This will be your "output folder". Publish from PhotoShop to the "output folder"
[this will create the gallery with the options you chose in the PhotoShop script. The thumbnail image files will be created directly proportional to the source images ie: they will be rectangular; but the gallery will display them in square frames]
3) Edit the "working folder" options.as file found in simpleviewer_pro\source\com\airtightinteractive\apps\viewers\simpleViewer\. Adjust "thumbnailWidth" and "thumbnailHeight". These refer to the thumbnail display area dimensions of the gallery, not the dimensions of the thumbnail files themselves. Set any other options you want to change.
4) Open the simpleviewer.fla file in Adobe Flash from the "working folder" simpleviewer_pro\source\. Publish (shift F12) - this will publish your options changes to the "working folder" simpleviewer_pro\web\viewer.swf.
5) Copy the viewer.swf from the "working folder" simpleviewer_pro\web\viewer.swf to the "output folder" from your PhotoShop publish. Overwrite the existing file.
6) Make any edits you want to the gallery.xml file in the "output folder" (NOT the "working folder")
7) Reload the index.html from the "output folder" to see your results. Each time you edit the gallery.xml file, you only have to reload the browser to see your results. Each time you edit the options.as file, you must republish from Flash to your "working folder", and overwrite the viewer.swf in your "output folder" to see your results.
8) To publish to the web, overwrite the viewer.swf and gallery.xml files on the server with the ones from the "output folder", as well as the images & thumbs folders.
Note - One more thing I had to figure out: about Background Color
The background color selected in the PhotoShop publish does not hold through republishing as pro gallery, if the published viewer.swf is separated from the original index.html for use in an actual website.
When I published the gallery from PhotoShop, I set the option for the gallery background color. This color displays as the background color of the index.html found in the output folder, and fills the entire space between the thumbs and main image, as expected. It seems this option is set as the background-color of this entire page in the published index.html.
However, the viewer.swf file itself does not have this background color, and it displays with the default dark charcoal gray background color when opened by itself in Flash Player, without the index.
When I replaced the viewer.swf and the gallery.xml as well as the thumbs & images folders on the server with the ones from the output folder - my gallery displayed just as it should (dimensions & arrangement), except for the gallery background color, which was back to the default.
I resolved this by making a swatch of the desired color, uploading it, and entering the image location in the xml file as backgroundImagePath=