ORIGINAL-- Currently running 6.3(4) on 525 FO configuration.
Tested conversion on 515 with a copy of our live config - noticed a few commands did not "port" over properly. Not a big problem - but a problem none the less.
Given that, here is my take on how to migrate: -Since we have a FO config - turn off SECONDARY and upgrade the PRIMARY. -Fix any issues, and run the PRIMARY for a few days. (Note: NO config changes are to be made during that period.) -If the are problems, turn off the PRIMARY and run the SECONDARY with the 6.3(4) code on it. Figure out what went wrong - downgrade the PRIMARY if necessary. -If all is well, turn off the PRIMARY and upgrade the SECONDARY.
Appreciate any and all feedback.