Thanks for the quick reply.
Is this the post? http://forum.mikrotik.com/t/using-restore-switches-rb2100-from-ap-to-cpe/62060/3
I have an RB450 here on v6rc5, so I tried making some changes and rebooting - the changes I made persisted.
I daren’t reboot the remote RB450 until I can be sure its settings will stick. I got v6rc6 ready - does the update process do anything that might help?