Printable Secret heart box small

I saw some secret heart boxes here on thingiverse but after trying to print various models, which all failed (due to being too flimsy), I gave up and designed my own.
The square pocket is 5x5x5 mm for a neodymium magnet which serves as a locking to a M3 steel nut.
The hinge needs a M3 threaded rod and both heart-parts need to be connected by a M4 bolt/washer/nut combination