No Mick, command is the same. Do you also have this in SD with 140.bin: Garmin\Updater\1371 with last folder containing your original boot bin renamed as Ldr.bin and a text file named update.txt containing only:
xrgn,140,1:/140.bin
reboot
without any quotes or spaces including at beginning or end of lines.
I have a vanilla AU2455 if you want any comparative tests done Mick.