Many thanks to everyone who contributed thoughts on this topic. I've assembled info from here and elsewhere into the first version of this list, published today on SoloPoly.net:
Non-primary partners tell how to treat us well
This is a living document, still a work in progress. So if you have anything further to add, or any feedback to that post, please either comment here, on my blog, or e-mail me at firstname.lastname@example.org
I worked really hard to include, and be respectful of, a variety of viewpoints here. I'd really like feedback on this post. Thanks!