Although I haven't tried it yet, I'm thinking only the one CAT5 is needed when talking to an XP-8. With the output option set to two-way trigger codes, and two-way transport set to Ethernet, I don't see why this wouldn't work for all commands to/from the RK3 (both two-way and one way). The IR output "signal" should not be used in this mode, as all triggers are sent via Ethernet to the XP-8.

Anyone try it?