Thanks, the box was made using set up scraps for the Portercable dovetail jig., hate to throw those away. Dialing in that jig takes quite a few trials.
I was printing PLA at 80% infill. Not using an impact driver, just a driver with a light touch , predrilling with vicks centering bits. The PLA being plastic will not take constant tension from the wedging action of the woodscrews over time. The layers will pull apart and creep. I have backed out the screws so that there is minimal interaction with the PLA.
I still believe the even 'more perfect hinge' would have flat bottomed counter sinks.
Kudos on getting the tolerances perfect in the hinge joint, they come off the printer and snap into action every time - even on my dinky IIIp printer. I just tried them when setting up a friend's Makerbot Z18 high-end printer this weekend and they are even more fantastic.
I intend on using your hinges in my engineering class as an exemplar of what good break-away design should look like.