I don't think you can do exactly what you are looking for with Emulate 5000 and Emulate 500.
The first reason is that the two emulators are separated by a decade of development and technology and don't work the same way. Emulate 5000 uses the Virtual Backplane and has access to serial ports, the RSLinx Classic and RSLinx Enterprise modules, and EtherNet/IP modules. Emulate 500 only has access to serial ports and the RSLinx Classic Emulate 500 driver.
The second reason is that the Emulate 5000 doesn't have a DHRIO module emulator. MSG instructions in ControlLogix go via CIP as far as the 1756-DHRIO and then are executed by the module as DH+.
What you *might* be able to do is change your messaging to run over DF1 serial ports, and physically connect multiple serial ports together with null-modem cables, or use virtual serial port pairs (there are software packages that do this).
Is you goal to test retry, trigger, heartbeat and data handling logic, or to evaluate throughput and performance ? I would expect the emulator to be better at the former than the latter.