I have contacted Kong and he is willing to support the R6400v2 if we can send him one.
We are raising money with a couple guys to send him one, see:
https://forum.dd-wrt.com/phpBB2/viewtopic.php?p=1138672#1138672
If you want his excellent build and support please contribute
I wasn't aware he can easily be contacted. I am guessing there are people who know people... that is a great start though.
Kong has made versions for the R6400v2 available, see:
https://forum.dd-wrt.com/phpBB2/viewtopic.php?t=316399