I appreciate all the helpful feedback. Especially from Brandt, who went the extra mile and sent me a small jpeg to illustrate the cropping ideas he and Scott were talking about. I've been checking out all the suggestions that were made, and each of them has merit and a certain appeal.
But in the end of course I had to decide what treatment best tells the story that I had in mind with this image. That story centered around the striking sequence of layers of sky atop layers of land, so I decided I needed to keep all of the sky. In this (last?) version, I started with version 2 and slightly desaturated the green layer at bottom and cropped off about half of it, which to my eye brings the land layers more into balance. Finally, following one of Brandt's suggestions, I used Content Aware Scaling to add a small amount of space on the right side, thereby providing a little more breathing room between the sunlit area and the edge of the frame.
Thanks again for taking the time to get involved.