Dual NVMe PCIe card?

I'm using a 5,1 with the latest (144.x) firmware, and OCLP booting into Sonoma and Monterey (and still have a drive with High Sierra). It has an RX 580, a Sonnet USB 3 card, and a single slot 4x NVMe PCIe adapter.

I'm wondering if this RIITOP (?) [dual NVMe adapter][https://www.riitop.com/products/dual-nvme-pcie-adapter-riitop-m-2-nvme-ssd-to-pci-e-3-1-x8-x16-card-support-m-2-m-key-nvme-ssd-22110-2280-2260-2242-2230] will work for my setup. The Amazon reviews say it does work with a Mac Pro, but they also mention that the installed NVMe drives are seen as external - but I don’t know if that’s with the latest firmware, the OCLP patches, etc.

I'm currently booting Monterey from a 970 Evo Plus 1TB NVMe drive on an [OWC Accelsior 1M2][https://www.owc.com/solutions/accelsior-1m2], and I'd love to swap in (2) 4TB NVMe drives and move Sonoma off of the SATA-II bus. (I have like 6.5 TB of SATA-II SSD storage, which is fine for many things, but for max performance I'd like to move my OS and app stack to the much, much faster PCIe bus...)

Doable? Bootable? Thanks!!