NetNewsWire on how they added iPhone Duo support:

How we did it: we didn’t do any work at all. We built the app using Xcode 27.1 and the default iOS SDK that comes with it, and that’s it. […]

There is a good list of reasons to use standard controls in the standard ways, and near the top of that list is to be ready for these kinds of days, so we’re not bogged down for a month or more trying to adapt to big changes like this.

Yep. Those of us who’ve suffered through Apple’s UI and platform transitions over the years have learned how painful it can be if you go your own way too much. Stick to what Apple’s trying to do, and you’ll be in better shape for the next shift. I learned this the hard way with Little Memory, but I’m so glad that I finally got it rewritten with my learnings, so my own iPhone Duo support wasn’t too difficult. There were some UX considerations for the outer vs inner screen layouts to optimize the experience, but they weren’t strictly necessary.