Multi Cam and Green Screen, Impossible?

Hi everyone! I've searched in vain for an answer to this the last few days to no avail. I've got a 9 camera multi cam sequence in Premier Pro CC 2018 shot on a green screen. In the "nest", I've pulled the key on each individual video and now have a black background on each in the Multi Cam sequence view. When I go back to the Project Panel to open the "nest", I figured I could just move each video track up and insert my background there, thus making it then visible in the Multi Cam sequence. This isn't working though as the Multi Cam sequence is seeing the additional backgrounds that I put in the nest as separate cameras. I can't figure out how to replace the backgrounds. Does anyone know how? I can do everything else in the nest and then see it in the Multi Cam sequence like color correction, using motion controls etc, but could really use some help. Thanks so much.