Dual stack IPv4/6 over IPv4 Site-to-site IPSEC VPN

I read the following guide:

https://help.fortinet.com/fos50hlp/52data/Content/FortiOS/fortigate-ipsecvpn-52/IPv6_and_IPsec/Site_Site_IPv6_over_IPv4_ex.htm#

The issue I have is that this only support single stack, either IPv4 or IPv6 across the IPSEC tunnel. 

If there any way to run dual-stack across the IPSEC tunnel?

Thanks.