I think it is not possible to back the image under 6.3(x) or older. You probably need to consider using the 6.3(5), with PDM 3.0(4). This is the highest version of 6.3(x) family available for download. Others are newer 7.x, or older 6.2(x)/6.1(x).
To delete your PDM, use "delete flash:" command. Use 'dir' command to verify the name. Deleting PDM can free spaces in your flash.
Refer to the following link for detail steps on upgrading (from monitor mode) and downgrading/reverting back to 6.3(x) code:
Login to the FXOS chassis manager.
Direct your browser to https://hostname/, and log-in using the user-name and password.
Go to Help > About and check the current version:
Check the current version availa...
We have configured the outside and inside Interface with official ipv6 adresses, set a default route on outside Interface to our router, we also have definied a rule , which also gets hits, to permit tcp from inside Interface to any6.
In Syslog I also se...