Well, they're done. All twenty-five of them!
I like the way the bases turned out, though I have to admit they didn't turn out to be the "invisible" bases I'd hoped for. And maybe the bases would look better if they were smaller - but that would have been a pain to do. Still, on my tabletop, you can definitely tell a grav tank from an ordinary tank, and that's what I wanted most. I'm not saying this is the perfect solution...just the one I chose.
One factor I hadn't considered was traction. Turns out that these clear bases are pretty slick on the bottom, and will easily "take a slider" to the bottom of the hill. This seems to be true only on non-flocked terrain.
The painting scheme seems colorful enough without being terribly out of place in the environment. And it was simple to accomplish - that's important to me, with limited time and too many miniatures. :-)
The various markings aren't as artistic as I might have liked, but they serve their purpose. (In the picture above, can you spot Green Leader? I thought you could.)