High Performance Backend - using HAProxy

Hi. I have enabled the HPB app, however NC is behind an LXC proxy, which is behind HAProxy, which is yet again behind another HAProxy on a public cloud instanse.

Internet → Public VM [HAProxy, then VPN from] → Server1 [HAProxy] → Server2 [LXC Proxy device, NC]

There is internally - Server1 and Server2 - configured DNS pointers for the hostnames, so trafic flows only on LAN between hosts (I got LDAP and other services running on other LXC containers, so all backend to backend aswell as internal clients when connected to LAN, never hits the public VM). Howeverthe automatic setup job of HPB fails, so I have to manually configure this. I have not yet dabbled much with HPB, hence I asks for help. Please.