In case someone is interested, I found an alternative to do the migration between different OS, using the mcdadmin command.
Although as Cisco says it shouldn't be used unless "guided" by the support.
To export
mcdadmin -e carconfig.txt
To import
mcdadmin -coi carconfig.txt
Also in CAR 5.0 I found a bug that caused me a few days of headache, in clients definition if you set the Ip address with slash (192.168.0.0/24) or range (192.168.0.1-254), then the aregcmd causes a segmentation fault and dump a core. The alternative is to set individual addresses or set a ip-address: 192.168.0.0 and netmask:255.255.255.0 filed. If you have recent backup you are lucky. If not...
Regards.