send SSL-VPN internet traffic through WAN interface of RED-connected second UTM?

Hi there,

i can't make this working - i hope you guys can help me :)

I have two UTMs which are connected through Sophos-RED. I'll call them UTM1 and UTM2.

I have set up a full-tunnel ssl-vpn on UTM2. This UTM2 does have a static ip address and is the RED-server.
UTM1 does not have a static IP address and is the RED-client.

Now, when i connect via ssl vpn client from anywhere to UTM2, i have the public IP-Address of UTM2 and can access all local machines and network from UTM1 over the RED-tunnel.
Works great so far.

But now i would like to do the following:
When i connect via ssl vpn client, i want all internet traffic to be routed through the RED-tunnel to use the WAN interface from UTM1.
so when i would check my ip-address it should show me the public ip from UTM1, and not the one from UTM2 anymore.

How can i make this work?

I tried setting up the RED-interface as a secondary wan interface and played around with multipath rules...
But i just can't get it to work. I'm missing something either on UTM1 and/or UTM2.

Any help or hint would be appreciated!

Thanks!

Cheers,

Max