Need Help reprogramming C-Payne MCIO PCIe gen5 Retimer Host Adapter

I recently purchased the adapter in hopes of connecting two P500X drives. By default it comes in x16 mode, but I’m looking to reprogram it to x8/x8. There is a provided i2c usb adapter that I have soldered to the adapter, but there is little instruction on how to achieve this. I read that another user was able to flash it via a bootable UEFI tool, but other than that I’m stuck. Any and all help would be appreciated.

Link to the adapter: MCIO PCIe gen5 Host Adapter x16 -RETIMER- – c-payne.com

Link to the referenced post: Solved: Working NVMe solution (Kioxia CM7-V (U.3) on OEM W790)