I've always wanted to see mavlink data on more than one device. I read through several pages, but had to try and fail. Visited blog entries Adrián Nagy hinst and Brit Davis. A little back and forth upgraded the firmware to my stanard 3dr robotics radio and it was not working, downgraded firmware and the radio worked normally only slave to a master. I think a little while and trying again. but now I updated just two radios, so I found the pattern. see picture and video.