IPv6 over IPv4 GRE with IPSec

Hi Rene
I use virtual tunnel interface and i seem to work, it is correct ?

IPv4 Crypto ISAKMP SA
dst             src             state          conn-id status
192.168.12.2    192.168.12.1    QM_IDLE           1002 ACTIVE
192.168.12.1    192.168.12.2    QM_IDLE           1001 ACTIVE

IPv6 Crypto ISAKMP SA

R1#sh crypto ipsec sa        

interface: Tunnel0
    Crypto map tag: Tunnel0-head-0, local addr 192.168.12.1

   protected vrf: (none)
   local  ident (addr/mask/prot/port): (192.168.12.1/255.255.255.255/47/0)
   remote ident (addr/mask/prot/port): (192.168.12.2/255.255.255.255/47/0)
   current_peer 192.168.12.2 port 500
     PERMIT, flags={origin_is_acl,}
    #pkts encaps: 256, #pkts encrypt: 256, #pkts digest: 256
    #pkts decaps: 245, #pkts decrypt: 245, #pkts verify: 245
    #pkts compressed: 0, #pkts decompressed: 0
    #pkts not compressed: 0, #pkts compr. failed: 0

Another question is how much mtu does IPsec Takes

Cordially