I ended up just using what Ryzen DRAM Calculator spat out...
That's where I started, but the suggested settings can't withstand even the mildest stress test. Extra voltage, if anything, makes things worse.
You can overclock the fclk to keep them in sync... Although if it is Micron e-die it probably won't tighten up too much.
fclk isn't available on Zen+, I thought. According to Thaiphoon.exe, my RAM is Samsung 8 Gb B-die (Boltzmann / 20 nm) / 1 die. But it's XMP timings- 3200MHZ @ 16-18-18-36-54- would suggest it's pretty crap B-die.
The only way I can boost the speed, it would appear, is to loosen the timings. Disabling GearDown equals instant BSOD, which does not help matters.
I'll give it one last try, then just enable XMP and never, ever mess with RAM tweaking again!!!!!