It's not technically a failure, but it is... instructive. 😕 The stack image is the prototypes with the earliest on top and "final" on bottom. The other shows the tab open. It works, but kinda in a "mission accomplished" sort of way. Jostling a box is likely to pop the tab out, so I don't achieve my desired tapeless solution. But, tape may hold this closed better than my existing straight flap. I can reengineer the tab with wings to stay closed, but that might be annoying to assemble. Erfh.