One option you can try is to compile the latest version of iPXE. There has been some updates to iPXE since 1.5.9 has been released. There may be some value in trying the process outlined by Sebastian here: https://forums.fogproject.org/post/141618
You will need the github version of the fog installer to follow these steps.
Remove the call to the fog.copydrivers and fog.updateunattended and insert your code. At this point in the code /ntfs has been mounted onto the windows (C: drive) partition, wherever it may be. The script takes into account nvme vs sata as well as partitions being in different order or locations.