I just wanted to report that
@pauldgroot 's 3D printed headband yoke assembly came in the mail today and I am happily using them on my HE560. They look very well made, glossier than the stock ones. They seem very durable. I tried putting some pressure on them with my hands and they seemed very rigid and flexible (I know those contradict a bit, but they are both - they seem to have potentially a better elastic modulus than the broken ones did from my test of the stock vs abs printed ones from my caveman pressure test). I'm pretty happy with them so far. They also smell very good! I don't know what Paul did with them, but they smell nice! haha!
I ran a set of calipers through two Hifiman yoke batches. The old broken one was 4.8mm as was the new "good" batch replacement I just received. Paul's 3D printed set was a tad thicker at 5.5mm at the location where my set snapped.
Anyway, my day job is to go out and audit and approve manufacture's of thermoplastic/thermoset composites suppliers for my company and I'll approve this one for use.
Thanks again for the set. I feel more confident handling these than I did with the previous two batches I had.