As an alternative, if you have a Linux box lying around you can build the idevicerestore project. I used the same SSD from m4-ssd.com and used the idevicerestore project to flash the drive. Some distros have the binary present but I found the the version distributed did not detect the newer M4 models. After building from source the M4 was recognized and I was able to flash.
https://github.com/libimobiledevice/idevicerestore