FWIW I've already tried loading a valid (created with FORMAT on the NABU) HFE file in the HxC software, then exporting it as a raw image. This raw image can be read ok by cpmtools. I then load this raw image back into the HxC software (using the settings from post #141) and export it again as an HFE, but that HFE doesn't then work on the NABU (shows a corrupt directory listing).
Per my post here, once the HFE is converted to a raw image all track format data is lost, only the sector 'user data' is retained. Converting it back to a HFE file won't recreate the lost data that is required by the NABU.