Per-Application L2 SpeedFusion Tunnel Settings

I am still learning Peplink features, so please forgive me if this is an obvious question. I have a L2 Speedfusion tunnel (between two MBX units) transporting a single VLAN. Because of the way the traffic is being handed to me, I have VoIP traffic and regular user web traffic in this same VLAN. Is there a way to enable WAN smoothing (or other SpeedFusion tunnel settings) only for the VoIP traffic (classified by port, src/dest, etc.)?

I know we can configure separate sub-tunnels with unique tunnel parameters, but my understanding is that traffic can only be directed between sub-tunnels by bridging each sub-tunnel to a unique VLAN. It would be great if I could direct certain traffic to sub-tunnels for the same VLAN, similar to how outbound policies can identify and direct traffic to different WANs.

I am pretty sure you create the different sub-tunnels, and then you use outbound policies to specify which traffic uses which sub tunnel. You can use any packet identification technique you want - src IP, dst port, etc. You aren’t limited to only VLan based routing since the outbound policies can be written using multiple different scopes.

That was my first plan, but it appears that layer 2 SpeedFusion tunnels aren’t “usable” in outbound policies. Or at least mine are not. Is this incorrect?