[Samba] Upgrading Samba

[henri transfert]

Hello all,

I've planned to upgrade a Samba DC from 4.6.7 to 4.9.4 .
For that I will use the following method :

   - build a new DC from 4.9.4 sources (on CentOS 7)
   - join this new DC to the domain
   - transfer the FSMO roles from the old DC (4.6.7) to the new DC (4.9.4)
   - replicate the sysvoldir from old DC to new DC
   - demote the old DC
   - switch off the old DC

Since I prefer to ask before facing any problems, is there any issue I
should take care about ? Especially from 4.6 to 4.9 release , is there any
big changes or incompatibility that could be a potential source of
troubles (Kerberos ? default values ?) ?
Would 4.8.8 a better seamless option ?

The smb.conf of the old DC is :
# Global parameters
[global]
        netbios name = OLD-DC
        realm = MYDOM.MYCOMP.COM
        workgroup = MYDOM
        dns forwarder = 1.2.3.4
        server role = active directory domain controller
        idmap_ldb:use rfc2307 = yes
        ldap server require strong auth = no
        ntlm auth = yes
        raw NTLMv2 auth = yes

[netlogon]
        path = /var/lib/samba/sysvol2/mydom.mycomp.com/scripts
        read only = No
        browseable = no

[sysvol]
        path = /var/lib/samba/sysvol2
        read only = No
        browseable = no

Thanks in advance for any advice.

Henri