Hi Ryan,
Glad you found the article useful. I've just looked at the version of SU I'm running (2013) and noticed I never bothered to install any of the plugins I was running on SU 8 (inc. Flattery). Likely this is because the new "Extension Warehouse" makes this a little difficult. Also, as I mentioned, I've been trying to force myself to learn Rhino, as that's the direction my design students are moving in.
So… I found this topic on the help forum which may help: http://help.sketchup.com/en/article/3000029
Title is "Migrating Plugins, Materials, and Components from previous versions" and discusses plugin compatibility with the new version.
As an alternative to Flattery, you might try Flatten Faces, which is in the Extension Warehouse (basically, the SU-approved plugin library). In SU, Window>Extension Warehouse, then type "Flatten Faces" into the search window. Disclaimer: I haven't tried Flatten Faces, but it looks like it will do more or less the same thing as Flattery.
I mostly use a Mac, but have Windows machines at work that run SU–I'll check tomorrow and see if I can find where the plugin files live.