Hit Ctrl shift alt g on the hunter screen.

Click the Video feed Tab. Make him the Source.
Load and then place it over where your kill shot pop up is displayed.
give it a name - hunterpop or something
Save as Auto so it comes up when wow is opened.

hit Ctrl shift alt g to close.

Go to the tank screen and hit Ctrl shift alt g to re-open.

Click the video feed tab and select viewer.
select hunterpop or whatever you named it. load and move to where you would like it on tank screen.

hit ctrl shift alt g to close.