IT seems that red5 suffers from a few issues in spark.
in Spark 2.0.8 it doesnt seem to auto pop-up a red5 window on the recieving end but audio starts streaming instantly.
No way for the recieving end to kill a conversation it seems.
Only way to stop streaming audio is to deny Flash access to my mic webcam.
seems like you can accidently start multiple Red5 sessions with the same person creating a weird audio echo issue and it starts to cause lag in the video.
I really like this plugin though and I think it has a lot of potential for spark.