Just tried with DS3617xs img + Jun's Loader v1.03b DS3617xs on a new USB drive,
Grub conf modified accordingly with new PID/VID/serial/(MAC unchanged)
New NAS was found via http://find.synology.com, followed the instructions to migrate and after reboot... nothing.
NAS is now unresponsive and not findable on the LAN. Got to start over I guess...