ok, stop overthinking this. set up the first deck like normal, using rs-422 9-pin vtr control. route the sdi out of that deck to the in on the second. now also route the rs-422 of the first deck out to the in of the second. now you have video, audio, and TC. on page 2 of the menu for the second deck, set TC in to RP188. This is the setup for a frame-accurate, on the fly crash clone. once your first deck starts recording, which should be in black, press rec-play on the second, and there you go, done.