The manual doesn't go much in depth regarding linking two R16's, it doesn't say anything about SD Cards, it says how to connect the two R16's with a USB cable and how to put them into a Master/slave state. The command keys on the master: play/record/FF/stop, will also control the slave. My trials show that Rog is right in assuming that each R16 must hold an SD, and when creating a new project it must be done on both the master and the slave!

Thanks for your help!