Can't install Win10 on M.2 RAID array, Taichi X399

Hi all. I've finally managed to use BIOS to set up a RAID 0 array comprising three M.2 NVMe drives.

I put the drivers onto a fresh Windows boot USB using EasyRAID. Windows started to install but the drivers selected from the same USB (put there by EasyRAID) didn't work.

Next, tried putting all the files from the setup floppy on the Asrock CD onto a separate USB. Same outcome.

Tried selecting all the drivers (not just 'bottom'), nothing. Sometimes the screen showing 'available boot drives' showed the three RAID drives separately, and sometimes nothing, but never the created array.

Looking at Bios, the drives are showing correctly as a RAID 0 array of the right size.

No other drives are connected, apart from a CD rom on port SATA_3 (left SATA 1 & 2 open for hard drives later).

The RAID installation manual states that for 32 bit W10, use I386 directory, for 64 bit, use AMD64 directory. I can't find these directories anywhere, not on the Windows boot drive nor the MB installation CD.

I can find the files mentioned during windows install, rcbottom.inf and rcraid.inf, in the USB drive's driver folder but they don't work.

I have checked the RAID driver version, fine, 9.0.0.88.

BIOS 3.5, identical Samsung M.2s, one graphics card.

I've set up quite a few RAID arrays in the past and never had such problems. I hope I'm doing something daft!