Connect Download Station to a different Virtual Switch / Ethernet Adapter

[kdb209]

A quick search didn't show an answer, so I guess I'll have to make a post ...

Is it possible to configure Download Station to use a particular Ethernet port?

I have a TVS-473e, which has 4 Ethernet ports.

I have it connected to two routers - the primary gateway connected to my main router and a second port connected to a second router which is connected under the first. The second router is running DD-WRT and I have it set up to connect to a VPN service. All the traffic through the DD-WRT router (whether wired or used as a wireless access point) is sent via the VPN, so I don't need to worry about running a VPN client on any devices connected to that router.

I would like to do Torrent and other downloads on my QNAP using the secondary Ethernet port connected to my secondary VPN router.

Is it possible to configure Download Station (and only download) to use that Ethernet adapter. I've created a virtual switch and connected it to the secondary ethernet port, but can't find any settings to tell Download Station to use that adapter. Is this possible?

If not, I guess I'll have to go with plan B and run a download client either in a docker or VM connected to the secondary port virtual switch.

Any suggestions?
Thanks.