Just in case anyone else wants to use these things with VLANs, I'm using mine on tagged ports now, after following the guide I think @Gingernut tried to link to (this one).
Rebased @sumo's repo on master with no other patches. No issues with performance that I can see. Getting 300 something Mbit/sec with iperf3.
Speaking of your repo @sumo, did you get anywhere with creating a PR?