@Lewscrew Great suggestions, thanks!
I simulated a 1/32", 6.2 degree taper ball nose in VCarve. (Based on one I found at Precise Bits). The results are somewhere between the 1/32" straight bit, and the 1/16" straight bit, decent, but not good enough for a chocolate mold:
The good news is that it's way faster. Total machining time is 1 hour 20 minutes (which I'm a little skeptical of, but I didn't scrutinize the feed rate of the taper ball).
The "User Larger Clearing Tool" option in VCarve is limited to the pocketing tool path. Since this is a 3D part, I instead used the "3D Rouging" tool path, followed by the "3D Finishing" tool path. I roughed it with a 1/8" square end mill, because if I use a 1/4" bit, the finishing tool path takes longer than the additional amount of time the 1/8" bit runs.
@jdg3 That's a good point. @JamesC's dies also have similarly small details, so clearly there is a way to cut this part with high quality. I recall @JamesC saying these take on average about 8 hours to cut, which is perfectly reasonable for a part like this, but also beyond the amount of free time that I have to spend running a test cut to help someone out right now (sorry!).