I have been busy with other stuff, so I am catching up to this topic.
When I got home, it turned out I only had one mono cable, so I couldn't try my daisy-chain theory.
For the record, I used to own a 970 but now have a 990, so this may not translate.
I connected a 1/8" mono from an "emitter" port form my Xantech distribution block to the IR-in on the 990. Then I connected a LED flasher to the IR-out on the 990. When I used the remote, the flasher blinked (as I expected). I then disconnected the cable going to the 990's IR-in and this time the flasher did not blink when using the remote via the IR sensor (as gonk suggested but not what I was wishing for).
It was a quick and dirty test, so take it for what it's worth.