Magic, thank you very much for the design! Yes, the "poles" are shifted compared to the other layers. I therefore rotated the die by 90 deg by setting the pole half way between points 0 and 1 and costructed the die from there.
Here comes another confirmation of your statement "the intuition that symmetry is always better is wrong in some cases". After having designed the D18, I ran my tools again over your D16, and, oops!, after some minutes a "better" solution popped up. I have kept my PC busy over the last 36 hours and I still keep getting better solutions, although progress is 4 digits after the comma... Current status is 49.63899330 deg compared to 49.62703013 deg.
My explanation is that in your design there are 2 rattlers (points that do not have minimum distance to any neighbor), as explained in my earlier post. Now there seems to be an even better solution if those neighbors are shifted closer towards the rattler and to distribute the "gained angle" over the rest of the configuration, thereby increasing the minimum distance (separation). The final version may thus no longer have the same symmetries. I uploaded the current best solution in my
applet 16 Points, PackAnti), there you see the configuration (coords and angle are in the report window).
Anyway, the difference to the contest winner is tiny, only about 0.02%, i.e., way below production tolerances. So this analysis is purley "alealogic" ... I will keep you posted.