[@Mercenary Lord] Probably for the best. I really like this concept for a bunch of reasons, and I'd hate to ruin it by getting too nitpicky. Tectonic plates are many kilometers thick, because they form part of the crust. So probably just the top layer of soil and bedrock forms the Isles.

If the plates are quite thick, which would mean plenty of resources, you could just say the Outreach centers are based in a pit mine, or one of the lower floating islets that surround the main Isles. Humans can adapt quite happily to high altitudes over the course of generations. (Could be maybe 2-3 thousand feet thick, floating that high in the air?)

Could also be a cool plot point - some resources are running out on the islands, so part of the missions is to find a new source. Would also mean that UI tech would be even more heavily slanted in favor of renewable sources. Heck with the Ring of Thunder I can see wind and hydro being their main sources of electricity quite easily.

While I'm at it - what kind of land is underneath the Isles? Just tell me if the questions are annoying and I'll cut it out, but I do like the technical bits of world building.