First FreeNAS build, stuck on ECC RDIMMs

[Frankenstein]

I'm starting my first FreeNas build with the Asrock D1521D4I, 2 WDred 4TB drives, SSD for boot, slog & power supply later... but I'm stuck trying to find the best RDIMMs for error correction (chip kill). Asrock's Memory QVL comes up short and I wonder if there's a longer list now that these boards have been out for a while?

I want to use at least 64GB of DDR4 ECC RDIMM but all I have found is 'HMA82GR7AFR4N-UH - SK Hynix 1x 16GB DDR4-2400 RDIMM PC4-19200T-R Single Rank x4'.
Please correct me if I'm mistaken, but don't I need at least a rank of x4? I'm not well versed with memory specifics yet...

Frankenstein

 

[Frankenstein]

...so I contacted AsrockRack support via their website and William replied with a better list for the D1521D4I than their memory QVL.
https://www.kingston.com/us/memory/search?DeviceType=8&Mfr=ASR&Line=Server Board&Model=97166
Starting with (2) 32G KSM24RD4/32MEI for 64GB which allows me to double it later if needed.