Uploading the stock ROM pulled from my MY2016 AT USDM FR-S (ZA1JF00D) in case anyone needs it.
Just flashed OFT stage 1 v4.03, it had a checksum error with the flash only definition I created (not sure why EcuFlash never asked for a checksum module in the definition creation wizard?
), so I flashed back to stock (without turning off the car) and tried again with Steve's K00G flash only xml from earlier in the thread with a few changes to suit my car and it worked great.
Big thanks to Steve!