As I mentioned when introducing the idea, my first draft of a pocket carrier for tiny airplanes wasn't quite successful. The slidey-lid didn't stay on. At all. But the second draft was much better, and the third was a complete success.
I abandoned the slide-over approach and went with a slide-all-around design, very much like a standard match box design. I had to add a curve to one side to introduce enough friction so it wouldn't accidentally open up.
Next step? Genericize the internal open areas to permit a range of plane designs to reside therein. It's time to be designing my own planes, not just using the design handed to me.
In the meantime I have plenty of those!