IPSEC VPN Tunnel to AWS using seconary public IP address

[blotditto]

Hello I'm very new to Fortiguard and we have a Fortiguard 200d on OS 5.4 that I am looking for a solution to.  I've searched high and low in the forums and cookbooks and cannot seem to find an answer to my scenario

We have 2 AWS IPSEC tunnels in a primary/secondary setup using the WAN interface public IP address that is working just fine with no issue that we setup using the documentation found on AWS.  We now have a second VCP in AWS that we would like to setup using the same configuration using one of our assigned public IP addresses.  I looked into using a VIP for this purpose but cannot for the life of me figure out how to assign the public IP address to the primary and secondary tunnel interfaces so that AWS see's the tunnel coming from the different public IP address rather than the public IP assigned to the WAN address.

Can someone point me to a possible document that covers such a scenario?

Thank you in advance.

Bill